How to read a tire size: P245/75R17 and LT285/70R17C

Width, aspect ratio, construction, rim size and the P/LT prefix.

The parts of P245/75R17

• P: P-metric passenger tire. LT means light truck, built for heavier loads and higher pressures. No prefix usually means a European metric size.
• 245: section width in millimeters.
• 75: aspect ratio; sidewall height is 75% of the width.
• R: radial construction.
• 17: rim diameter in inches.

A trailing letter such as the C in LT285/70R17C is the load range (C, D, E…), which sets the maximum load and inflation pressure.

Flotation sizes

Off-road sizes such as 31x10.50R15LT give overall diameter (31") and width (10.5") in inches, then the rim size.

Load and speed

The service description after the size, such as 109S, is the load index (109 = 2,271 lb per tire) and speed rating (S = 112 mph). Replacement tires should meet or exceed the original load index.

The tire size your vehicle was built with is on the door-jamb placard. Different trims of the same model year often use different sizes.

Look it up by vehicle

• Chevrolet Silverado 1500 tire sizes
• Ford F-150 tire sizes
• Honda Civic tire sizes
• Jeep Wrangler tire sizes
• Toyota Tacoma tire sizes

Last reviewed 2026-10-14.