About TireSizeCompare

TireSizeCompare is a free calculator that compares two tire sizes from their sidewall codes — diameter, width, sidewall, circumference, revolutions per mile and speedometer error — without sign-up or tracking.

How it works

Every figure on this site comes from the size code and the standard formulas: diameter = rim (in) × 25.4 + 2 × (width × aspect ratio ÷ 100); circumference = π × diameter; revolutions per mile = 63,360 ÷ diameter (in). Flotation sizes (such as 31x10.50R15) state diameter and width in inches directly. No manufacturer's catalogue data is used, and the calculations run in your browser or are pre-computed when each page is published.

Limits

Size codes are nominal: real tires vary slightly between brands and models, and tread wear changes diameter over a tire's life. A comparison here tells you what the codes mean, not what will fit your vehicle. Clearance, wheel width range, load index and speed rating all matter — confirm any size change against your vehicle manual or a professional tire shop before buying.

Who runs it

TireSizeCompare is part of a small family of free, single-purpose tools built and maintained by ORBITFRAME. The same family is linked in the footer of every page. A Pro tier ($9/mo) is planned for saved comparisons and bulk fitment work; it is not yet on sale and nothing on this site asks for payment.