Quick Answer
- A metric size gives the width in mm and the aspect ratio: 315/70R17 is 34.4 in tall and 12.4 in wide. Diameter = rim + 2 x width x aspect / 100 / 25.4.
- For an inch size such as 35x12.50R17 the closest metric sizes are 305/75R17 (35.0 in), 325/70R17 (34.9 in), 285/80R17 (35.0 in). The 315/70R17 people quote is 0.6 in shorter than 35.
- These are arithmetic equivalents. No manufacturer publishes an official table converting inch sizes to metric sizes, so check the tire maker's published diameter, load rating and your clearance.
Enter a metric size such as 315/70R17 to get its overall diameter and width in inches.
315/70R17 in inches
Overall diameter
34.36 in
873 mm
Section width
12.40 in
315 mm
Sidewall
8.68 in
221 mm
Inch style label
34.4x12.4R17
calculated
Calculated from the size code. The overall diameter a maker publishes for a real tire can differ by a few tenths of an inch.
Get a plain-English explanation of your results and what they mean for your vehicle.
Metric to Standard Tire Size Chart (Inches)
Overall diameter, width and sidewall in inches for common truck and SUV metric sizes, calculated from the size code.
| Metric size | Diameter (in) | Width (in) | Sidewall (in) | Inch style label |
|---|---|---|---|---|
| 245/75R16 | 30.47" | 9.65" | 7.23" | 30.5x9.6R16 |
| 265/70R16 | 30.61" | 10.43" | 7.30" | 30.6x10.4R16 |
| 265/70R17 | 31.61" | 10.43" | 7.30" | 31.6x10.4R17 |
| 265/75R16 | 31.65" | 10.43" | 7.82" | 31.6x10.4R16 |
| 275/65R18 | 32.07" | 10.83" | 7.04" | 32.1x10.8R18 |
| 275/70R17 | 32.16" | 10.83" | 7.58" | 32.2x10.8R17 |
| 285/70R17 | 32.71" | 11.22" | 7.85" | 32.7x11.2R17 |
| 285/75R16 | 32.83" | 11.22" | 8.42" | 32.8x11.2R16 |
| 285/75R17 | 33.83" | 11.22" | 8.42" | 33.8x11.2R17 |
| 295/70R18 | 34.26" | 11.61" | 8.13" | 34.3x11.6R18 |
| 295/75R16 | 33.42" | 11.61" | 8.71" | 33.4x11.6R16 |
| 305/55R20 | 33.21" | 12.01" | 6.60" | 33.2x12.0R20 |
| 305/65R18 | 33.61" | 12.01" | 7.81" | 33.6x12.0R18 |
| 305/70R17 | 33.81" | 12.01" | 8.41" | 33.8x12.0R17 |
| 305/70R18 | 34.81" | 12.01" | 8.41" | 34.8x12.0R18 |
| 315/70R17 | 34.36" | 12.40" | 8.68" | 34.4x12.4R17 |
| 315/75R16 | 34.60" | 12.40" | 9.30" | 34.6x12.4R16 |
| 325/65R18 | 34.63" | 12.80" | 8.32" | 34.6x12.8R18 |
| 335/65R18 | 35.15" | 13.19" | 8.57" | 35.1x13.2R18 |
For revolutions per mile of any size see the revolutions per mile calculator, and for two sizes side by side the tire size comparison calculator.
Inches to Metric Tire Size Chart (35x12.50R17 and Other Sizes)
The two closest metric sizes for common inch sizes, ranked by overall diameter and then width. Nothing is an exact match.
| Inch size | Closest metric | Diameter | Next closest | Diameter |
|---|---|---|---|---|
| 31x10.50R15 | 255/80R15 | 31.1" | 275/75R15 | 31.2" |
| 33x12.50R15 | 305/75R15 | 33.0" | 325/70R15 | 32.9" |
| 33x10.50R17 | 255/80R17 | 33.1" | 275/75R17 | 33.2" |
| 33x12.50R17 | 315/65R17 | 33.1" | 335/60R17 | 32.8" |
| 33x11.50R20 | 275/60R20 | 33.0" | 295/55R20 | 32.8" |
| 35x10.50R17 | 255/90R17 | 35.1" | 285/80R17 | 35.0" |
| 35x12.50R17 | 305/75R17 | 35.0" | 325/70R17 | 34.9" |
| 35x12.50R18 | 305/70R18 | 34.8" | 335/65R18 | 35.1" |
| 35x12.50R20 | 315/60R20 | 34.9" | 295/65R20 | 35.1" |
| 35x12.50R22 | 325/50R22 | 34.8" | 305/55R22 | 35.2" |
| 37x12.50R17 | 315/80R17 | 36.8" | 335/75R17 | 36.8" |
| 37x13.50R20 | 335/65R20 | 37.1" | 355/60R20 | 36.8" |
The flotation tire size converter and the tire size converter and comparator cover the same ground from other angles.
How Metric and Inch Tire Sizes Work
| Part | Meaning |
|---|---|
| P, LT, ST, T or none | Tire type. BFGoodrich: P is passenger metric, LT light truck, T temporary spare and ST special trailer. A tire with no letter is a euro metric size. |
| Width (315) | Section width in millimetres, from the widest point of the outer sidewall to the widest point of the inner sidewall (BFGoodrich). |
| Aspect ratio (70) | The sidewall height as a percentage of the width (Michelin, Bridgestone, BFGoodrich). A 315/70 has a sidewall 70% as tall as it is wide. |
| R | Radial construction. D is diagonal and B is belted (BFGoodrich). |
| Rim (17) | The wheel diameter in inches the tire fits. |
| Inch (flotation) size | In a size such as 35x12.50R17 the calculator reads the first number as the nominal overall diameter in inches, the second as the section width in inches and the last as the rim diameter. We found no manufacturer publication that defines this, so treat it as the convention used here. |
Metric to inches
Sidewall (in) = width x aspect / 100 / 25.4, diameter = rim + 2 x sidewall. For 315/70R17: sidewall 8.68 in, diameter 34.36 in, width 12.40 in.
Inches to metric
Width (mm) = section width in inches x 25.4. Aspect = ((diameter - rim) / 2 x 25.4) / width x 100. For 35x12.50R17: width 318 mm, sidewall 229 mm, so an aspect near 72, between 70 and 75 in the standard series.
Why it is only close
Metric aspect ratios come in steps of 5 and widths in steps of 10 mm, so no metric size matches an inch size exactly: 315/70R17 is 34.4 in and 315/75R17 is 35.6 in against a nominal 35.
Check the real tire
Tire makers publish the measured overall diameter of each tire. A nominal 35 inch tire often measures a little under 35 inches, so use the published figure for gearing, speedometer and clearance work.
Sources: BFGoodrich, How to Read a Tire Sidewall; Michelin USA and Bridgestone, how to read a tire size.
How to Use the Metric Tire Calculator
- 1To go from a metric size to inches, open Metric to Inches and type a size such as 315/70R17. You get the overall diameter, section width and sidewall in inches.
- 2To go from an inch size to metric, open Inches to Metric and type a size such as 35x12.50R17. You get the closest metric sizes ranked by diameter, then width.
- 3Compare the diameter difference in inches and percent, and the width difference in mm, for each match.
- 4Use the tire maker's published diameter, check the load index, and confirm clearance before buying.