Wheel Speed Calculator

The conversion used

Wheel rpm depends on two things: how fast you're travelling and how far the wheel moves in one rotation, its rolling circumference. From your tyre size the overall diameter is rim × 25.4 + 2 × (width × profile ÷ 100) in millimetres, and circumference is diameter × π. Wheel rpm is then (speed × revs per mile) ÷ 60, and the reverse works the same way in the other direction. There's no estimation in either step; both numbers follow directly from your tyre's dimensions.

Why wheel rpm isn't engine rpm

This is deliberately a smaller, standalone question than "what rpm is my engine doing at 70 mph." That question also needs the gear ratio and final drive, because the gearbox and differential change the rotation speed between the engine and the wheel. If that's what you're after, use the gear ratio speed calculator, which takes this same tyre geometry and adds the drivetrain on top. This page answers the simpler question of what the wheel itself is doing, useful on its own for prop-shaft speeds, ABS and speed-sensor checks, or just satisfying curiosity about how hard a tyre is actually spinning.

Where this number matters

Wheel rpm is what an ABS or wheel-speed sensor is actually measuring, multiplied by its tone ring's tooth count to produce a pulse frequency. It's also the number that matters for checking a tyre's rated speed against sustained high-rpm use (track days, rolling roads), and for anyone fitting a speedometer sender, cable drive, or aftermarket gauge that reads directly off wheel rotation rather than road speed. At 70 mph a typical 245/45R17 tyre is turning at a little over 900 revolutions every minute, more than 15 times a second.

What this tool doesn't check

Circumference is calculated from nominal tyre dimensions; real rolling radius shrinks a little under load, at speed, and as the tyre wears, so an ABS sensor's true reading will differ slightly from this figure. It also assumes both wheels on an axle are turning at the same speed, which isn't true mid-corner. A tyre size mismatch front-to-rear can also throw this off; check with the tyre size comparator if you're running different sizes.