Speedometer Gear Calculator
Result
Speedometer Tire Size Correction Calculator: calculate estimated actual speed (km/h) from the supplied inputs.
Formula
- Model: indicated speed × replacement rolling diameter / original rolling diameter. Idealized estimate assuming speedometer calibrated for original diameter; actual rolling circumference and manufacturer speedometer tolerance may differ. Inputs should be within meaningful physical ranges.
- The main inputs are Displayed speed, Original tire diameter, New tire diameter. Enter them in the units and format shown in the calculator.
- Use the units, labels and assumptions shown beside each input so the formula is applied consistently.
- Changing any input above recalculates the result with the same calculation engine used by this page.
Example: Speedometer Gear
- Displayed speed: 90 km/h
- Original tire diameter: 600 mm
- New tire diameter: 660 mm
Using Displayed speed (km/h) = 90, Original tire diameter (mm) = 600, New tire diameter (mm) = 660, result: Estimated actual speed (km/h) = 99.
Sample result: Calculating…
Frequently asked questions
What does the Speedometer Gear calculate?
Speedometer Tire Size Correction Calculator: calculate estimated actual speed (km/h) from the supplied inputs.
Which values should I enter?
Enter Displayed speed, Original tire diameter, New tire diameter using the units and format shown beside each field.
What formula does this calculator use?
The calculator uses the following relationship: indicated speed × replacement rolling diameter / original rolling diameter.
Why might my result differ from another source?
Results can differ when another source uses different units, rounding rules, conventions or assumptions. Compare the inputs and definitions before comparing results.
Does the result update automatically?
Yes. Changing an input updates the result using the same calculation engine shown on this page.