Tyre Size Calculator NZ
Compare up to four tyre sizes side by side. Handles metric, imperial and the legacy numeric sizes most calculators cannot read, including 7.50R16, 9R15 and 31x10.5R15, with real replacement options for each.
Add a legacy, truck, agricultural or industrial size 100 sizes
Truck, agricultural and industrial sizes are shown for dimensions only. Speedometer and WOF output is hidden for them, because neither applies to a tractor or a forklift tyre. Sizes marked bias are cross ply and are not interchangeable with a radial of the same code.
| Your speedo reads | Actual speed (T2) | Actual speed (T3) | Actual speed (T4) |
|---|
Potentially suitable alternatives, matched on overall diameter only. Diameter is one of several things that decide whether a size is legal and safe on your vehicle.
| Size | Diameter | Sidewall | Width | Rim |
|---|
How to read a tyre size
Every tyre size is a formula. Once you know how it works you can read the real dimensions of any tyre straight off the sidewall, and understand why two tyres marked the same size are not always the same size.
What this calculator can and cannot read
Four different sizing systems are still in use on New Zealand roads. The calculator handles three of them from the numbers alone. The fourth needs a standards table, and we hold that table for the common sizes but not for every one.
- 205/55R16 metric, any width and profile
- 175R13 no profile, read as 82 series
- 31/10.5R15 imperial and flotation
- Vintage numeric such as 5.60-15 and 6.00-16
- US alphanumeric such as F70-14 and G78-15
- Metric rim and TRX such as 165R400 and 190/65R390
- Light truck and commercial, 6.00R16 through 9.00R16
- Truck and bus, R20, R22.5 and R24.5
- Agricultural, forklift and earthmoving
- Sizes outside the 103 we hold published dimensions for
- Bias codes written with a dash, such as 7.50-16, where we hold the radial only
- Anything where the code alone cannot give a unique diameter
A legacy code carries no profile, so its dimensions have to come from a published standard or a named manufacturer reference rather than a formula. Where we hold that reference the calculator uses it and says so. Where we do not, it tells you instead of showing a number it cannot stand behind.
See size crossoversReading 225/40R18
- 225Section width in millimetres.
- 40Aspect ratio. The sidewall height as a percentage of the width, not a measurement in millimetres.
- RRadial construction.
- 18Rim diameter in inches.
The profile number is the part that catches people out. A 40 does not mean 40mm. It means the sidewall is 40 percent as tall as the tyre is wide, so the same profile number gives a different sidewall height on every width.
Reading 31/10.50R15
- 31Overall diameter in inches. This is the whole tyre, not the width.
- 10.50Section width in inches.
- 15Rim diameter in inches.
Imperial sizing works the opposite way round to metric. Metric gives you the width and makes you calculate the height. Imperial gives you the height directly and makes you calculate the sidewall. Nothing is a percentage, so there is no profile to convert.
31/10.50R15 is the most common imperial size in our own workshop archive, documented on 15 inspected tyres. It is a 787mm tall tyre on a 15 inch rim, which is why it looks so much larger than the 4x4 metric sizes it sits alongside.
The number is nominal, not a measurement
225/40R18 does mean the tyre is nominally 225mm wide. But nominal is a design target, not a promise about the tyre in your hand. Two tyres both marked 225 can measure differently, for three reasons.
- BrandEvery manufacturer moulds to its own target inside the permitted tolerance, so section width varies between brands and between patterns from the same brand.
- RimSection width is quoted on a nominated measuring rim. Fit the same tyre to a wider rim and it gets wider. As a rule of thumb the section width moves by roughly 5mm for every half inch of rim width.
- ShapeTread pattern, shoulder design and sidewall construction all change the moulded profile, so two tyres with identical numbers can sit differently in the guard.
This is why the alternates table above quotes the standard measuring rim for each size. Our figures are calculated from the published sizing standard rather than measured off any single brand, so they are a consistent basis for comparison rather than a claim about a specific tyre.
For anything where a few millimetres matter, such as guard clearance, suspension travel, a modified build or a certification, calculated figures are not enough. Get the dimensions from the manufacturer's technical data for that exact model and size. That is the only authoritative source, and it is the one we use ourselves when a fitment is marginal.
Reading 175R13
Some sizes have no profile number at all. 175R13 is not an error and it is not missing information: the profile is left off because the tyre is a full profile, the tallest shape in normal use. Written out in modern form it is 175/80R13.
The profile you fill in is 82, not 80. This is worth being precise about because a lot of calculators use 80, presumably because it is a rounder number, and it quietly makes every one of these sizes come out too small.
Take a 185R14C, a size sold by the thousand on vans and trailers. Published data gives it a 660mm overall diameter and a 152mm sidewall. Now test both candidates: 185 × 0.82 = 151.7mm, which rounds to the published 152mm. 185 × 0.80 = 148mm, which does not. Run the diameters and 82 gives 659mm against a published 660mm, while 80 gives 651mm. A 175R13 checks out the same way at 144mm.
So 82 it is, and that is what this calculator uses. On a 175R13 the two answers differ by about 8mm, roughly 1.3 percent. It will not decide whether a tyre fits, but it will show up when you compare our figures against a tool that rounded to 80.
These are still common on older light commercials, vans and trailers. We list 29 of them, and 185R14 is the most common.
Reading 7.50R16
- 7.50A nominal inch-coded size designation. Related to width historically, but it is not a measurement.
- RRadial construction. Written with a dash instead, as 7.50-16, it means bias or crossply, which is a genuinely different tyre.
- 16Nominal rim diameter code in inches.
This is the oldest of the systems and the one that catches people out most, because it looks like the imperial sizes in Part 2 but behaves completely differently. In 31/10.50R15 the first number is the height of the tyre. In 7.50R16 the first number relates to the width. And unlike both other systems, nothing in the code tells you the profile at all.
There is no hidden percentage you can apply to work these out. The codes came from a historical sequence of nominal widths rather than from any height-to-width formula, so the dimensions had to be preserved in standards tables instead. Work backwards from those tables and the effective ratio lands at 91.3 percent on a 7.50R16 but 95.8 percent on a 6.50R16. There is no single number that works across the family, which is why any tool offering you a neat conversion for these sizes is estimating and should say so.
The coded number is not the width
Compare what the code says against the design width of the same tyre. This is Part 3's point in its most extreme form: the gap here is far larger than anything on a modern metric tyre.
- 6.50Code converts to 165mm. Design width is 182mm, about 10 percent wider.
- 7.00Code converts to 178mm. Design width is 202mm, about 14 percent wider.
- 7.50Code converts to 191mm. Design width is 220mm, about 15 percent wider.
- 8.25Code converts to 210mm. Design width is 241mm, about 15 percent wider.
So converting 7.50 to 190.5mm is fine for looking a tyre up, but it is the wrong number to use for clearance. A data book may show 8.1, 8.4 or 8.7 inches for different 7.50R16 patterns.
The 20 inch and 22.5 inch families
Truck sizes show the pattern much more clearly than light vehicle ones. The older tube type 20 inch sizes and the tubeless 22.5 inch sizes were designed to stand at the same heights, which is why the diameters line up exactly:
| Older 20 inch | Diameter | Matching 22.5 inch | Diameter |
|---|---|---|---|
| 9.00R20 | 1,019mm | 10R22.5 | 1,019mm |
| 10.00R20 | 1,054mm | 11R22.5 | 1,054mm |
| 11.00R20 | 1,085mm | 12R22.5 | 1,085mm |
These are not swaps. A 20 inch tyre and a 22.5 inch tyre need different wheels, so you cannot move between the columns without changing rims. What the table shows is that the two families were laid out to cover the same standing heights, which is useful when you are working out what a vehicle originally ran or comparing an old fleet spec against a modern one.
You will also see 11.00R22.5 written on some tyres. The standards write it as 11R22.5 and they are the same size. This calculator accepts either.
Three codes that look alike and are not
- 9.5R15Nominal inch size, 15 inch rim, and the most ambiguous code on this page. It is not a reliable standard identifier. In New Zealand listings it usually means the agricultural implement tyre 9.5L-15, which stands about 767mm tall, but the same code is also used for the LT numeric road size that stands about 825mm. That is a 58mm difference, so we hold both and label them separately rather than quietly pick one. Check the full sidewall before you order.
- 30×9.5R15A high flotation size. Here 30 is the overall diameter in inches and 9.5 is the width, so it can be worked out. This is a different tyre from 9.5R15 and the two must never be shortened into each other.
- 9.5L-15The bias implement series, about 767mm tall on an 8.00 rim. This is what a plain 9.5R15 usually turns out to be. The numbers resembling the others does not make it equivalent.
Where we hold the standardised dimensions for a numeric size, the calculator uses them and says so. Where we do not, it tells you that instead of inventing a figure. For a fitment where millimetres matter, the tyre maker's data book for that exact pattern and load range is the only authoritative source.
Replacing a legacy size: what fits instead
If you have just bought something wearing 7.50R16 or 31/10.5R15, the problem is rarely the maths. It is that the size is hard to find and you need to know what else will work. These charts answer that directly. Each one starts from the standard dimensions of the legacy size, then lists the closest alternatives, and shows you three things about each: how the diameter compares, how much wider or narrower it is, and how much more or less profile you end up with.
Read the diameter column first, because that is what changes your speedometer and gearing. Within about 2 percent is a straight swap. Between 2 and 5 percent will usually fit but will shift the speedometer slightly. Beyond 5 percent, treat it as a change rather than a replacement.
Then read across. A size can match on diameter and still be a poor swap if it is 80mm wider, because that is what fouls guards and suspension. The profile column tells you how the ride will change: a much lower number means a shorter, stiffer sidewall than the tyre you are replacing.
Legacy sizes do not carry a profile in the code, so the figure quoted for them is an effective profile worked back from the standard dimensions. It is there so you can compare like with like against a modern size. It is not printed on the tyre and is not part of the designation.
16 inch legacy numeric sizes
The old light truck and commercial sizes. In most cases there is a modern metric 16 inch size within a percent or two on diameter, so you can usually keep the wheels. Watch the width column though, because the modern equivalents are almost always wider.
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 16 inch, keep your wheels | ||||
| 205/85R16 | 755mm0% | 205mm+23mm | 85-10.8 | Quote this size → |
| 235/75R16 | 759mm+0.5% | 235mm+53mm | 75-20.8 | Quote this size → |
| 215/80R16 | 750mm-0.7% | 215mm+33mm | 80-15.8 | Quote this size → |
| 245/70R16 | 749mm-0.8% | 245mm+63mm | 70-25.8 |
Shop from $140
|
| 255/70R16 | 763mm+1.1% | 255mm+73mm | 70-25.8 |
Shop from $210
|
| 225/75R16 | 744mm-1.5% | 225mm+43mm | 75-20.8 |
Shop from $175
|
| 17 inch | ||||
| 215/75R17 | 754mm-0.1% | 215mm+33mm | 75-20.8 | Quote this size → |
| 245/65R17 | 750mm-0.7% | 245mm+63mm | 65-30.8 |
Shop from $175
|
| 255/65R17 | 763mm+1.1% | 255mm+73mm | 65-30.8 |
Shop from $195
|
| 235/65R17 | 737mm-2.4% | 235mm+53mm | 65-30.8 |
Shop from $160
|
| 15 inch | ||||
| 265/70R15 | 752mm-0.4% | 265mm+83mm | 70-25.8 | Quote this size → |
| 315/60R15 | 759mm+0.5% | 315mm+133mm | 60-35.8 | Quote this size → |
| 235/75R15 | 734mm-2.8% | 235mm+53mm | 75-20.8 |
Shop from $180
|
| 215/75R15 | 704mm-6.8% | 215mm+33mm | 75-20.8 |
Shop from $165
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 16 inch, keep your wheels | ||||
| 265/70R16 | 777mm-0.1% | 265mm+63mm | 70-22 |
Shop from $210
|
| 285/65R16 | 777mm-0.1% | 285mm+83mm | 65-27 | Quote this size → |
| 235/80R16 | 782mm+0.5% | 235mm+33mm | 80-12 | Quote this size → |
| 245/75R16 | 774mm-0.5% | 245mm+43mm | 75-17 |
Shop from $210
|
| 215/85R16 | 772mm-0.8% | 215mm+13mm | 85-7 |
Shop from $270
|
| 17 inch | ||||
| 265/65R17 | 776mm-0.3% | 265mm+63mm | 65-27 |
Shop from $200
|
| 245/70R17 | 775mm-0.4% | 245mm+43mm | 70-22 | Quote this size → |
| 255/65R17 | 763mm-1.9% | 255mm+53mm | 65-27 |
Shop from $195
|
| 285/65R17 | 802mm+3.1% | 285mm+83mm | 65-27 |
Shop from $265
|
| 15 inch | ||||
| 265/75R15 | 778mm0% | 265mm+63mm | 75-17 | Quote this size → |
| 285/70R15 | 780mm+0.3% | 285mm+83mm | 70-22 | Quote this size → |
| 235/75R15 | 734mm-5.7% | 235mm+33mm | 75-17 |
Shop from $180
|
| 215/75R15 | 704mm-9.5% | 215mm+13mm | 75-17 |
Shop from $165
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 16 inch, keep your wheels | ||||
| 235/85R16 | 806mm-0.2% | 235mm+15mm | 85-6.3 |
Shop from $300
|
| 285/70R16 | 805mm-0.4% | 285mm+65mm | 70-21.3 | Quote this size → |
| 265/75R16 | 804mm-0.5% | 265mm+45mm | 75-16.3 |
Shop from $215
|
| 275/70R16 | 791mm-2.1% | 275mm+55mm | 70-21.3 |
Shop from $190
|
| 17 inch | ||||
| 235/80R17 | 808mm0% | 235mm+15mm | 80-11.3 | Quote this size → |
| 315/60R17 | 810mm+0.2% | 315mm+95mm | 60-31.3 | Quote this size → |
| 265/70R17 | 803mm-0.6% | 265mm+45mm | 70-21.3 |
Shop from $265
|
| 285/65R17 | 802mm-0.7% | 285mm+65mm | 65-26.3 |
Shop from $265
|
| 285/70R17 | 831mm+2.8% | 285mm+65mm | 70-21.3 |
Shop from $315
|
| 15 inch | ||||
| 340/60R15 | 789mm-2.4% | 340mm+120mm | 60-31.3 | Quote this size → |
| 320/70R15 | 829mm+2.6% | 320mm+100mm | 70-21.3 | Quote this size → |
| 235/75R15 | 734mm-9.2% | 235mm+15mm | 75-16.3 |
Shop from $180
|
| 215/75R15 | 704mm-12.9% | 215mm-5mm | 75-16.3 |
Shop from $165
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 16 inch, keep your wheels | ||||
| 295/75R16 | 849mm-1.2% | 295mm+54mm | 75-18.9 | Quote this size → |
| 255/85R16 | 840mm-2.2% | 255mm+14mm | 85-8.9 | Quote this size → |
| 315/75R16 | 879mm+2.3% | 315mm+74mm | 75-18.9 |
Shop from $330
|
| 285/75R16 | 834mm-2.9% | 285mm+44mm | 75-18.9 |
Shop from $255
|
| 305/70R16 | 833mm-3% | 305mm+64mm | 70-23.9 |
Shop from $310
|
| 17 inch | ||||
| 285/75R17 | 859mm0% | 285mm+44mm | 75-18.9 | Quote this size → |
| 305/70R17 | 859mm0% | 305mm+64mm | 70-23.9 | Quote this size → |
| 285/70R17 | 831mm-3.3% | 285mm+44mm | 70-23.9 |
Shop from $315
|
| 265/70R17 | 803mm-6.5% | 265mm+24mm | 70-23.9 |
Shop from $265
|
| 285/65R17 | 802mm-6.6% | 285mm+44mm | 65-28.9 |
Shop from $265
|
| 15 inch | ||||
| 320/70R15 | 829mm-3.5% | 320mm+79mm | 70-23.9 | Quote this size → |
| 340/60R15 | 789mm-8.1% | 340mm+99mm | 60-33.9 | Quote this size → |
| 235/75R15 | 734mm-14.6% | 235mm-6mm | 75-18.9 |
Shop from $180
|
| 215/75R15 | 704mm-18% | 215mm-26mm | 75-18.9 |
Shop from $165
|
15 inch legacy sizes
Fifteen inch is the confusing one, because two completely different legacy systems are still in circulation and they look alike at a glance.
- 9R15LT numeric. The number is the width in inches. These run close to a 92 percent profile, which makes them surprisingly tall.
- 30/9.50R15Flotation. The first number is the overall diameter in inches and the second is the width.
A 9R15 is 801mm tall. A 30/9.50R15 is 762mm tall. The one with the smaller number on the sidewall is the bigger tyre, by nearly 40mm. If you read a 9R15 as though it were a flotation size you will fit something 5 percent too small, and if you go the other way you will fit something too big for the guards. Check which system you are looking at before anything else.
Each size below shows options on three rim diameters, because the legacy 15 inch sizes are tall and the modern 15 inch range does not always reach them. Moving up a rim size usually gives a closer match as well as more choice.
Worth ruling out rather than leaving you wondering. The tallest 14 inch tyre in common supply is about 700mm, and these legacy sizes run from 762mm to 872mm. Even against the smallest of them, a 30/9.50R15, the best 14 inch option is 8 percent short, and against a 10.5R15 it is more than 20 percent short. Going down to 14 inch is not a practical route from any of these.
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 340/60R15 | 789mm-1.5% | 340mm+111mm | 60-32 | Quote this size → |
| 285/70R15 | 780mm-2.6% | 285mm+56mm | 70-22 | Quote this size → |
| 265/75R15 | 778mm-2.9% | 265mm+36mm | 75-17 | Quote this size → |
| 235/75R15 | 734mm-8.4% | 235mm+6mm | 75-17 |
Shop from $180
|
| 215/75R15 | 704mm-12.1% | 215mm-14mm | 75-17 |
Shop from $165
|
| 225/70R15 | 696mm-13.1% | 225mm-4mm | 70-22 |
Shop from $130
|
| 16 inch | ||||
| 265/75R16 | 804mm+0.4% | 265mm+36mm | 75-17 |
Shop from $215
|
| 280/70R16 | 798mm-0.4% | 280mm+51mm | 70-22 | Quote this size → |
| 235/85R16 | 806mm+0.6% | 235mm+6mm | 85-7 |
Shop from $300
|
| 275/70R16 | 791mm-1.2% | 275mm+46mm | 70-22 |
Shop from $190
|
| 17 inch | ||||
| 285/65R17 | 802mm+0.1% | 285mm+56mm | 65-27 |
Shop from $265
|
| 245/75R17 | 799mm-0.2% | 245mm+16mm | 75-17 | Quote this size → |
| 265/70R17 | 803mm+0.2% | 265mm+36mm | 70-22 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 320/70R15 | 829mm+0.5% | 320mm+79mm | 70-22 | Quote this size → |
| 340/60R15 | 789mm-4.4% | 340mm+99mm | 60-32 | Quote this size → |
| 285/70R15 | 780mm-5.5% | 285mm+44mm | 70-22 | Quote this size → |
| 235/75R15 | 734mm-11% | 235mm-6mm | 75-17 |
Shop from $180
|
| 215/75R15 | 704mm-14.7% | 215mm-26mm | 75-17 |
Shop from $165
|
| 225/70R15 | 696mm-15.6% | 225mm-16mm | 70-22 |
Shop from $130
|
| 16 inch | ||||
| 305/70R16 | 833mm+1% | 305mm+64mm | 70-22 |
Shop from $310
|
| 285/75R16 | 834mm+1.1% | 285mm+44mm | 75-17 |
Shop from $255
|
| 235/85R16 | 806mm-2.3% | 235mm-6mm | 85-7 |
Shop from $300
|
| 17 inch | ||||
| 305/65R17 | 828mm+0.4% | 305mm+64mm | 65-27 | Quote this size → |
| 285/70R17 | 831mm+0.7% | 285mm+44mm | 70-22 |
Shop from $315
|
| 265/70R17 | 803mm-2.7% | 265mm+24mm | 70-22 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 320/70R15 | 829mm-2.4% | 320mm+66mm | 70-22 | Quote this size → |
| 340/60R15 | 789mm-7.1% | 340mm+86mm | 60-32 | Quote this size → |
| 285/70R15 | 780mm-8.1% | 285mm+31mm | 70-22 | Quote this size → |
| 235/75R15 | 734mm-13.5% | 235mm-19mm | 75-17 |
Shop from $180
|
| 215/75R15 | 704mm-17.1% | 215mm-39mm | 75-17 |
Shop from $165
|
| 225/70R15 | 696mm-18% | 225mm-29mm | 70-22 |
Shop from $130
|
| 16 inch | ||||
| 295/75R16 | 849mm0% | 295mm+41mm | 75-17 | Quote this size → |
| 255/85R16 | 840mm-1.1% | 255mm+1mm | 85-7 | Quote this size → |
| 285/75R16 | 834mm-1.8% | 285mm+31mm | 75-17 |
Shop from $255
|
| 305/70R16 | 833mm-1.9% | 305mm+51mm | 70-22 |
Shop from $310
|
| 315/75R16 | 879mm+3.5% | 315mm+61mm | 75-17 |
Shop from $330
|
| 17 inch | ||||
| 295/70R17 | 845mm-0.5% | 295mm+41mm | 70-22 | Quote this size → |
| 255/80R17 | 840mm-1.1% | 255mm+1mm | 80-12 | Quote this size → |
| 285/70R17 | 831mm-2.1% | 285mm+31mm | 70-22 |
Shop from $315
|
| 265/70R17 | 803mm-5.4% | 265mm+11mm | 70-22 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 320/70R15 | 829mm-4.9% | 320mm+53mm | 70-22 | Quote this size → |
| 340/60R15 | 789mm-9.5% | 340mm+73mm | 60-32 | Quote this size → |
| 285/70R15 | 780mm-10.6% | 285mm+18mm | 70-22 | Quote this size → |
| 235/75R15 | 734mm-15.8% | 235mm-32mm | 75-17 |
Shop from $180
|
| 215/75R15 | 704mm-19.3% | 215mm-52mm | 75-17 |
Shop from $165
|
| 225/70R15 | 696mm-20.2% | 225mm-42mm | 70-22 |
Shop from $130
|
| 16 inch | ||||
| 315/75R16 | 879mm+0.8% | 315mm+48mm | 75-17 |
Shop from $330
|
| 295/75R16 | 849mm-2.6% | 295mm+28mm | 75-17 | Quote this size → |
| 285/75R16 | 834mm-4.4% | 285mm+18mm | 75-17 |
Shop from $255
|
| 305/70R16 | 833mm-4.5% | 305mm+38mm | 70-22 |
Shop from $310
|
| 17 inch | ||||
| 315/70R17 | 873mm+0.1% | 315mm+48mm | 70-22 | Quote this size → |
| 285/75R17 | 859mm-1.5% | 285mm+18mm | 75-17 | Quote this size → |
| 285/70R17 | 831mm-4.7% | 285mm+18mm | 70-22 |
Shop from $315
|
| 265/70R17 | 803mm-7.9% | 265mm-2mm | 70-22 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 255/75R15 | 764mm+0.3% | 255mm+14mm | 75-4 | Quote this size → |
| 295/65R15 | 764mm+0.3% | 295mm+54mm | 65-14 | Quote this size → |
| 240/80R15 | 765mm+0.4% | 240mm-1mm | 80+1 | Quote this size → |
| 235/75R15 | 734mm-3.7% | 235mm-6mm | 75-4 |
Shop from $180
|
| 215/75R15 | 704mm-7.6% | 215mm-26mm | 75-4 |
Shop from $165
|
| 225/70R15 | 696mm-8.7% | 225mm-16mm | 70-9 |
Shop from $130
|
| 16 inch | ||||
| 255/70R16 | 763mm+0.1% | 255mm+14mm | 70-9 |
Shop from $210
|
| 235/75R16 | 759mm-0.4% | 235mm-6mm | 75-4 | Quote this size → |
| 215/85R16 | 772mm+1.3% | 215mm-26mm | 85+6 |
Shop from $270
|
| 245/75R16 | 774mm+1.6% | 245mm+4mm | 75-4 |
Shop from $210
|
| 17 inch | ||||
| 275/60R17 | 762mm0% | 275mm+34mm | 60-19 | Quote this size → |
| 235/70R17 | 761mm-0.1% | 235mm-6mm | 70-9 | Quote this size → |
| 255/65R17 | 763mm+0.1% | 255mm+14mm | 65-14 |
Shop from $195
|
| 245/65R17 | 750mm-1.6% | 245mm+4mm | 65-14 |
Shop from $175
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 340/60R15 | 789mm+0.3% | 340mm+73mm | 60-16 | Quote this size → |
| 285/70R15 | 780mm-0.9% | 285mm+18mm | 70-6 | Quote this size → |
| 265/75R15 | 778mm-1.1% | 265mm-2mm | 75-1 | Quote this size → |
| 235/75R15 | 734mm-6.7% | 235mm-32mm | 75-1 |
Shop from $180
|
| 215/75R15 | 704mm-10.5% | 215mm-52mm | 75-1 |
Shop from $165
|
| 225/70R15 | 696mm-11.6% | 225mm-42mm | 70-6 |
Shop from $130
|
| 16 inch | ||||
| 275/70R16 | 791mm+0.5% | 275mm+8mm | 70-6 |
Shop from $190
|
| 235/80R16 | 782mm-0.6% | 235mm-32mm | 80+4 | Quote this size → |
| 265/70R16 | 777mm-1.3% | 265mm-2mm | 70-6 |
Shop from $210
|
| 245/75R16 | 774mm-1.7% | 245mm-22mm | 75-1 |
Shop from $210
|
| 17 inch | ||||
| 255/70R17 | 789mm+0.3% | 255mm-12mm | 70-6 | Quote this size → |
| 275/65R17 | 789mm+0.3% | 275mm+8mm | 65-11 | Quote this size → |
| 265/65R17 | 776mm-1.4% | 265mm-2mm | 65-11 |
Shop from $200
|
| 285/65R17 | 802mm+1.9% | 285mm+18mm | 65-11 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 320/70R15 | 829mm+2% | 320mm+28mm | 70-4 | Quote this size → |
| 340/60R15 | 789mm-3% | 340mm+48mm | 60-14 | Quote this size → |
| 285/70R15 | 780mm-4.1% | 285mm-7mm | 70-4 | Quote this size → |
| 235/75R15 | 734mm-9.7% | 235mm-57mm | 75+1 |
Shop from $180
|
| 215/75R15 | 704mm-13.4% | 215mm-77mm | 75+1 |
Shop from $165
|
| 225/70R15 | 696mm-14.4% | 225mm-67mm | 70-4 |
Shop from $130
|
| 16 inch | ||||
| 235/85R16 | 806mm-0.9% | 235mm-57mm | 85+11 |
Shop from $300
|
| 285/70R16 | 805mm-1% | 285mm-7mm | 70-4 | Quote this size → |
| 265/75R16 | 804mm-1.1% | 265mm-27mm | 75+1 |
Shop from $215
|
| 305/70R16 | 833mm+2.5% | 305mm+13mm | 70-4 |
Shop from $310
|
| 17 inch | ||||
| 255/75R17 | 814mm+0.1% | 255mm-37mm | 75+1 | Quote this size → |
| 315/60R17 | 810mm-0.4% | 315mm+23mm | 60-14 | Quote this size → |
| 265/70R17 | 803mm-1.2% | 265mm-27mm | 70-4 |
Shop from $265
|
| 285/65R17 | 802mm-1.4% | 285mm-7mm | 65-9 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 320/70R15 | 829mm-1.1% | 320mm+2mm | 70-1.9 | Quote this size → |
| 340/60R15 | 789mm-5.8% | 340mm+22mm | 60-11.9 | Quote this size → |
| 285/70R15 | 780mm-6.9% | 285mm-33mm | 70-1.9 | Quote this size → |
| 235/75R15 | 734mm-12.4% | 235mm-83mm | 75+3.1 |
Shop from $180
|
| 215/75R15 | 704mm-16% | 215mm-103mm | 75+3.1 |
Shop from $165
|
| 225/70R15 | 696mm-16.9% | 225mm-93mm | 70-1.9 |
Shop from $130
|
| 16 inch | ||||
| 255/85R16 | 840mm+0.2% | 255mm-63mm | 85+13.1 | Quote this size → |
| 285/75R16 | 834mm-0.5% | 285mm-33mm | 75+3.1 |
Shop from $255
|
| 305/70R16 | 833mm-0.6% | 305mm-13mm | 70-1.9 |
Shop from $310
|
| 235/85R16 | 806mm-3.8% | 235mm-83mm | 85+13.1 |
Shop from $300
|
| 17 inch | ||||
| 255/80R17 | 840mm+0.2% | 255mm-63mm | 80+8.1 | Quote this size → |
| 285/70R17 | 831mm-0.8% | 285mm-33mm | 70-1.9 |
Shop from $315
|
| 265/70R17 | 803mm-4.2% | 265mm-53mm | 70-1.9 |
Shop from $265
|
| Size | Diameter | Width | Profile | |
|---|---|---|---|---|
| 15 inch, keep your wheels | ||||
| 320/70R15 | 829mm-6.7% | 320mm+2mm | 70-9.9 | Quote this size → |
| 340/60R15 | 789mm-11.2% | 340mm+22mm | 60-19.9 | Quote this size → |
| 285/70R15 | 780mm-12.3% | 285mm-33mm | 70-9.9 | Quote this size → |
| 235/75R15 | 734mm-17.4% | 235mm-83mm | 75-4.9 |
Shop from $180
|
| 215/75R15 | 704mm-20.8% | 215mm-103mm | 75-4.9 |
Shop from $165
|
| 225/70R15 | 696mm-21.7% | 225mm-93mm | 70-9.9 |
Shop from $130
|
| 16 inch | ||||
| 315/75R16 | 879mm-1.1% | 315mm-3mm | 75-4.9 |
Shop from $330
|
| 295/75R16 | 849mm-4.5% | 295mm-23mm | 75-4.9 | Quote this size → |
| 285/75R16 | 834mm-6.2% | 285mm-33mm | 75-4.9 |
Shop from $255
|
| 305/70R16 | 833mm-6.3% | 305mm-13mm | 70-9.9 |
Shop from $310
|
| 17 inch | ||||
| 315/70R17 | 873mm-1.8% | 315mm-3mm | 70-9.9 | Quote this size → |
| 285/75R17 | 859mm-3.4% | 285mm-33mm | 75-4.9 | Quote this size → |
| 285/70R17 | 831mm-6.5% | 285mm-33mm | 70-9.9 |
Shop from $315
|
| 265/70R17 | 803mm-9.7% | 265mm-53mm | 70-9.9 |
Shop from $265
|
Matching diameter, width and profile gets you a tyre that fits and drives right. It does not tell you the tyre can carry the vehicle. Compare the load index and load range as well, which matters most on utes, vans, trailers and anything that tows. Check that your existing rim falls inside the new size's approved width range, and check clearance at full lock and full suspension travel rather than just standing still.
Not sure what you have, or want us to confirm a swap before you commit? Send us the size or a photo of the sidewall and we will tell you what fits.
Metric. sidewall = width x profile / 100, then diameter = (rim x 25.4) + 2 sidewalls.
Imperial. The first number is already the diameter in inches, so sidewall = (diameter - rim) / 2.
Legacy numeric. No formula exists. The code carries no aspect ratio, so these come from standards tables, not calculation.
A size with no profile, such as 175R13, is an 82 series tyre. Plenty of calculators use 80 because it is a rounder number, which makes every one of these sizes come out about 1.3 percent small.
Published data settles it. A 185R14C is 660mm overall with a 152mm sidewall. 185 x 0.82 = 151.7mm and gives 659mm. 185 x 0.80 = 148mm and gives 651mm.
We hold published dimensions for 103 legacy and unusual sizes, covering vintage numeric, US alphanumeric, metric rim and TRX, light commercial, conventional and 15 degree truck, agricultural, forklift and earthmoving.
Every one comes from a published standard or a named manufacturer reference, and each was cross-checked before it went in. Anything outside that set is declined rather than estimated, because the code alone does not contain enough information to produce a unique overall diameter.
Sizes are matched on overall diameter. Whether a tyre is legal and safe on your vehicle also depends on rim width, load index, speed rating, matching across an axle, clearance under lock and compression, and whether the change needs LVV certification.
Speedometer figures show the effect of the size change alone. WOF guidance references the NZTA Vehicle Inspection Requirements Manual.
Dimensions are calculated from published sizing standards, not measured from individual tyres, and real products vary from the standard design figures. This is highly reliable but hand-compiled and not guaranteed to be error-free. If you spot anything wrong, email email@tyredispatch.co.nz and we will correct it. Questions about sizing? Get in touch or call (07) 573 9090.
