Tire size calculator
A tire size like 225/65R17 102H says the tire is 225 mm wide, its sidewall is 65% of that width, it is a radial for a 17-inch wheel, it carries up to 1,874 lb, and it is rated to 130 mph. Type the size from your sidewall to decode it.
- Tire type
- Euro-metric passenger tire (no letter in front)
- Section width
- 225 mm (8.86 in)
- Aspect ratio
- 65: the sidewall is 65% as tall as the tire is wide
- Sidewall height
- 146 mm (5.76 in)
- Construction
- R: radial construction
- Wheel (rim) diameter
- 17 in
- Overall diameter
- 28.52 in (724 mm)
- Circumference
- 89.6 in
- Revolutions per mile
- 707 (439 per km)
- Load index
- 102: up to 1,874 lb (850 kg) per tire
- Speed rating
- H: up to 130 mph (210 km/h)
Thinking of a different size? Compare it with your current tires →
Changing sizes? Compare two tire sizes → Full charts: speed ratings and load index.
How to read a tire (tyre) size
Every part of the code means something. Here is 225/65R17 102H taken apart, the way the calculator does it:
| Tire type | Euro-metric passenger tire (no letter in front) |
|---|---|
| Section width | 225 mm (8.86 in) |
| Aspect ratio | 65: the sidewall is 65% as tall as the tire is wide |
| Sidewall height | 146 mm (5.76 in) |
| Construction | R: radial construction |
| Wheel (rim) diameter | 17 in |
| Overall diameter | 28.52 in (724 mm) |
| Circumference | 89.6 in |
| Revolutions per mile | 707 (439 per km) |
| Load index | 102: up to 1,874 lb (850 kg) per tire |
| Speed rating | H: up to 130 mph (210 km/h) |
Overall diameter = wheel diameter + 2 x sidewall height, where sidewall = width x aspect ratio. Revolutions per mile = 63,360 inches / circumference.
Common speed ratings
| S | 112 mph | 180 km/h |
|---|---|---|
| T | 118 mph | 190 km/h |
| H | 130 mph | 210 km/h |
| V | 149 mph | 240 km/h |
| W | 168 mph | 270 km/h |
| Y | 186 mph | 300 km/h |
Common load indexes
| 91 | 1,356 lb | 615 kg |
|---|---|---|
| 94 | 1,477 lb | 670 kg |
| 98 | 1,653 lb | 750 kg |
| 102 | 1,874 lb | 850 kg |
| 104 | 1,984 lb | 900 kg |
| 107 | 2,150 lb | 975 kg |
| 112 | 2,469 lb | 1,120 kg |
| 116 | 2,756 lb | 1,250 kg |
Keep the new tires at the right pressure
The pressure to run is on the placard in the driver's door jamb, not the maximum printed on the tire. Check it cold, once a month.
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Torquing the wheels back on? Lug nut torque specs by vehicle →
Frequently asked
What does 225/65R17 mean on a tire?
225 is the section width in millimeters, 65 is the aspect ratio (the sidewall is 65% as tall as the tire is wide), R means radial construction, and 17 is the wheel diameter in inches. A 225/65R17 tire is about 28.5 inches tall overall.
What do the numbers and letter after the tire size mean?
They are the load index and the speed rating. In 225/65R17 102H, 102 means each tire can carry up to 1,874 lb (850 kg), and H means it is rated for up to 130 mph (210 km/h).
What is the difference between P and LT tires?
A P in front of the size marks a P-metric passenger tire. LT marks a light truck tire, built for heavier loads and higher pressures. A size with no letter in front is a Euro-metric passenger tire. Replace LT tires with LT tires.
Where do I find my car's tire size?
On the placard on the driver's door jamb, in the owner's manual, and on the sidewall of the tires on the car. The placard gives the size, load index and speed rating the car was built with, plus the cold inflation pressure.
Can I use a different tire size?
Tire shops commonly keep a new size within about 3% of the original overall diameter, with a load index and speed rating at least as high as the original. Use the tire size comparison calculator to see the difference and the speedometer error.
Load index and speed rating values are the published standard tables, each value checked against two sources: Wikipedia: Tire code (load index and speed rating tables, citing ETRTO); Tyreteam: load index and speed category tables (kg, km/h); BFGoodrich: tire speed ratings; Bridgestone: tire speed rating; Pirelli: tire load index (US pound chart). Dimensions are calculated from the size itself and are nominal: a tire's measured size varies slightly by brand and wheel width.