Tire Size Converter

Metric to inches, flotation to metric, and real sizes with the same diameter on other wheels.

Set up for: what a size means, in inches · Different situation?

Metric (265/70R17 or 2657017) or flotation (35x12.50R20)

Where do I find my size?

It's on the tire sidewall, e.g. P265/70R17 115T, and on the tire placard sticker on the driver's door jamb (also in the owner's manual). The placard shows the size the vehicle came with; the sidewall shows what is fitted now. If they differ, use the placard as your starting point. Digits are enough here: 2657017 or 33125020.

Popular flotation sizes in metric

35x12.50R20 in metric35.0 in tall33x12.50R20 in metric33.0 in tall31x10.50R15 in metric31.0 in tall35x12.50R17 in metric35.0 in tall33x12.50R18 in metric33.0 in tall35x12.50R18 in metric35.0 in tall33x12.50R17 in metric33.0 in tall33x12.50R22 in metric33.0 in tall33x12.50R15 in metric33.0 in tall35x12.50R22 in metric35.0 in tall37x12.50R17 in metric37.0 in tall37x12.50R20 in metric37.0 in tall

FAQ

How do I convert a metric tire size to inches?

Diameter (in) = wheel size + 2 × (width mm × aspect ratio ÷ 100) ÷ 25.4. Width (in) = width mm ÷ 25.4. For 265/70R17: 265 × 0.70 = 185.5 mm sidewall, 17 + 2 × 185.5 ÷ 25.4 = 31.6 in.

How do I convert a flotation size like 35x12.50R20 to metric?

A flotation size already gives the diameter (35 in) and width (12.5 in). To find a metric equivalent, look for metric sizes on the same wheel with about the same diameter; the converter lists the real sizes within 3%.

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.