The parts, left to right
| Part | Example | Meaning |
|---|---|---|
| Type letters | P, LT, ST | P = passenger car, LT = light truck, ST = special trailer. No letters usually means a metric passenger size (Euro-metric). |
| Section width | 265 | Width of the tire in millimetres, sidewall to sidewall. |
| Aspect ratio | 70 | Sidewall height as a percent of the width: 70% of 265 mm. |
| Construction | R or ZR | R = radial. ZR is an older marking for high-speed radials. |
| Wheel diameter | 17 | Wheel (rim) diameter in inches. |
| Load index | 94 | A number for the weight the tire can carry; see the load index chart. |
| Speed rating | T | A letter for the top speed the tire is rated for: see the speed rating chart. |
| DOT code | DOT … 2223 | The last four digits are the week and year it was made; see the date code reader. |
Worked example: 265/70R17 94T
| Step | Math | Result |
|---|---|---|
| Sidewall | 265 × 70% = 185.5 mm ÷ 25.4 | 7.30 in |
| Overall height | 17 + 2 × 7.30 | 31.61 in |
| Width | 265 ÷ 25.4 | 10.43 in |
| Revs per mile | 63,360 ÷ (π × height) | 638.1 |
Other formats
You may also see flotation sizes like 33x12.50R15: height, width and wheel, all in inches. The calculator reads both, plus forms like 265 70 17, 265/70-17 and LT285/75R16. For the conversion, see tire sizes in inches.
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.