Tire Revolutions per Mile

Free Tire Revolutions per Mile calculator with clear step-by-step results.

About Tire Revolutions per Mile

Revolutions per mile is the inverse of rolling circumference and is what drives speedometer calibration, ABS wheel-speed comparison and odometer accuracy. Comparing a new tyre's circumference against the original gives the scale error introduced by the change.

Formulas

Revolutions per mile

Revs = 1,609,344 mm per mile / rolling circumference mm

Speedometer error

Error % = (new circumference / original circumference - 1) x 100

Worked example

With the default values below, Tire Revolutions per Mile returns Revolutions per mile of 785.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Rolling circumferenceminimum 200 mm: 2,050 mm
Original tyre rolling circumferenceminimum 200 mm: 2,000 mm
Indicated speedminimum 1 km/h: 100 km/h

Results

Revolutions per mile: 785.0 rev/mile
Revolutions per kilometre: 487.8 rev/km
True speed at that indication: 102.50 km/h
Speedometer error: 2.50% %

Step by step

1Values used
2Revolutions per mile
3Speedometer error
4Revolutions per mile= 785.0 rev/mile
5Revolutions per kilometre= 487.8 rev/km
6True speed at that indication= 102.50 km/h
7Speedometer error= 2.50 %

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Changing tyre size affects speedometer accuracy, odometer readings, ABS and stability control calibration, and may breach vehicle construction and use regulations or insurance conditions.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Changing tyre size affects speedometer accuracy, odometer readings, ABS and stability control calibration, and may breach vehicle construction and use regulations or insurance conditions.

Frequently Asked Questions

Which way does the error go?

A larger circumference means fewer revolutions for the same distance, so the speedometer under-reads and you are travelling faster than indicated.

How much error is acceptable?

Most regulations allow a speedometer to over-read but never under-read. Keeping a tyre change within about 1.5% of the original circumference avoids problems.