# How to read a tire size

Type the code from your sidewall, or read the example below.

## Quick answer

In **P225/65R17 102H**: P = passenger tire, 225 = width in mm, 65 = sidewall height as a % of width, R = radial, 17 = wheel diameter in inches, 102 = load index (1,874 lb per tire), H = speed rating (130 mph).

## Each part of the code

| Part | Example | Meaning |
| --- | --- | --- |
| Tire type | P | P = passenger, LT = light truck, none = European metric (similar to P, slightly different load tables), T = temporary spare |
| Section width | 225 | Width in millimeters, sidewall to sidewall |
| Aspect ratio | 65 | Sidewall height as a percentage of width |
| Construction | R | R = radial; D or B = bias-ply (rare on cars) |
| Rim diameter | 17 | Wheel diameter in inches |
| Load index | 102 | Max load per tire: 850 kg / 1,874 lb ([chart](/tools/tire-load-index-chart)) |
| Speed rating | H | Max sustained speed: 130 mph ([chart](/tools/tire-speed-rating-chart)) |

## Where else to find the right size

Your car's correct size and pressure are on the placard inside the driver door jamb (sometimes the glove box or fuel door) and in the owner's manual. Use that size, not just what is on the car now: a previous owner may have fitted something else.

## Other markings on the sidewall

- **DOT code:** ends in four digits for the week and year made (e.g. 2324 = week 23 of 2024). Most makers advise replacing tires 6-10 years after manufacture regardless of tread.
- **UTQG:** treadwear (e.g. 500), traction (AA-C) and temperature (A-C) grades for comparing tires.
- **M+S / 3PMSF:** mud and snow, and the three-peak mountain snowflake for severe snow performance.
- **Max press:** the most the tire can hold, not the pressure to run. Use the door placard.

## Frequently asked questions

### What does the R in a tire size mean?

R means radial construction, where the cords inside run across the tire from bead to bead. Almost every passenger tire sold today is radial; it does not stand for rim.

### Is a higher load index better?

Only up to a point: it must be at least what your car's placard specifies. A higher load index is safe but can ride slightly firmer; a lower one is not safe because the tire may be overloaded.

### Can I use a lower speed rating than my original tires?

It is not recommended. Fitting a lower speed rating can reduce handling and high-speed safety, and some insurers and tire shops will not do it. Match or exceed the original rating.

## Popular sizes

- [245/75R16](https://diagxcar.com/tools/tire-size/245-75r16)
- [265/75R16](https://diagxcar.com/tools/tire-size/265-75r16)
- [285/75R16](https://diagxcar.com/tools/tire-size/285-75r16)
- [215/45R17](https://diagxcar.com/tools/tire-size/215-45r17)
- [215/55R17](https://diagxcar.com/tools/tire-size/215-55r17)
- [215/60R17](https://diagxcar.com/tools/tire-size/215-60r17)
- [225/45R17](https://diagxcar.com/tools/tire-size/225-45r17)
- [225/50R17](https://diagxcar.com/tools/tire-size/225-50r17)
- [225/55R17](https://diagxcar.com/tools/tire-size/225-55r17)
- [225/60R17](https://diagxcar.com/tools/tire-size/225-60r17)
- [225/65R17](https://diagxcar.com/tools/tire-size/225-65r17)
- [235/65R17](https://diagxcar.com/tools/tire-size/235-65r17)

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Source page: https://diagxcar.com/tools/tire-size-decoder
General information, not a substitute for a qualified mechanic.