Tire Size Calculator & Comparison

Type your current and new tire sizes to see the difference in height, width and speedometer reading.

e.g. 265/70R17 or 33x12.50R20

 

Tire size converterMetric ↔ inches ↔ flotation, equivalentsTire size chart507 sizes with diameters33-inch tires in metricAnd 30–37 inch sizesSpeedometer calculatorActual speed after a size change

Popular tire size comparisons

275/55R20 vs 33x12.50R20+3.4% diameter315/70R17 vs 35x12.50R17+1.9% diameter265/75R16 vs 31x10.50R15−2.1% diameter275/60R20 vs 33x12.50R20±0.0% diameter285/70R17 vs 33x12.50R17+0.9% diameter275/60R20 vs 35x12.50R20+6.1% diameter275/70R18 vs 33x12.50R18−0.5% diameter285/70R17 vs 35x12.50R17+7.0% diameter315/70R17 vs 37x12.50R17+7.7% diameter265/70R17 vs 35x12.50R17+10.7% diameter265/75R15 vs 31x10.50R15+1.1% diameter275/65R18 vs 33x12.50R18+2.9% diameter

All 150 comparisons

Popular sizes

265/70R1731.6 in tall · 10.4 in wide275/55R2031.9 in tall · 10.8 in wide285/70R1732.7 in tall · 11.2 in wide275/60R2033.0 in tall · 10.8 in wide275/70R1833.2 in tall · 10.8 in wide315/70R1734.4 in tall · 12.4 in wide265/75R1631.6 in tall · 10.4 in wide205/55R1624.9 in tall · 8.1 in wide285/75R1632.8 in tall · 11.2 in wide275/65R1832.1 in tall · 10.8 in wide225/65R1728.5 in tall · 8.9 in wide225/45R1725.0 in tall · 8.9 in wide

FAQ

How do you compare two tire sizes?

Work out each tire's overall diameter from its size code (wheel size + 2 × sidewall height), then compare: the % difference in diameter is also the % change in speedometer reading and in the distance covered per wheel turn. This calculator does it live as you type.

What does the ±3% rule mean?

Many tire shops use ±3% overall diameter as a rule of thumb for a replacement size. It is not a manufacturer or legal limit, and it doesn't cover wheel fit, clearance, load index or speed rating. More on the 3% rule.

Why do real tires measure differently?

The size code gives a nominal size. Maker data books list real tires in the same size up to about 1.5% apart, and flotation sizes are usually a little under their name. Nominal vs actual diameter.

Important: These are calculated (nominal) dimensions, not a fitment recommendation. Real tires of the same size differ by brand and model (makers allow about ±3% of section height), and width changes with the rim it is mounted on. The math can't see wheel width and offset, clearance at full steering lock and suspension travel, load index, speed rating, or what your vehicle maker approves. Before changing size, check your door-jamb placard and owner's manual and ask a tire professional. A replacement tire must meet or exceed the load index and speed rating on the placard.