About

This site converts a metric tire size into the dimensions people actually compare: overall diameter, section width, sidewall height, circumference and revolutions per mile, in both inches and millimetres.

Every number here is computed from the sidewall code. There is no chart behind it and no dataset that can go stale — a tire size states its own dimensions, and the arithmetic is four lines long. The one place converters commonly go wrong is the divisor: it is 2540, not 2550, and the difference grows with diameter.

What this site deliberately does not do is tell you which size fits your vehicle. That depends on rim width, load and speed ratings and clearance, none of which are in the sidewall code, and the data that maps a vehicle to its factory size is licensed.