Estimate road speed from engine speed, drivetrain ratio and tire diameter.
RMP Calculator
Results
Wheel RPM
0
Vehicle speed
0
Table of Contents
1
What is RMP Calculator?
2
How to Use This Calculator
- Enter or select Engine RPM, Drivetrain transmission ratio, Tire diameter.
- Check the unit beside each measurement. For a percentage or rate, use the scale and time period stated in the form.
- Choose Calculate, then compare the output with the formula and example below. If you change a value or option, calculate again to update the result.
3
Formula Used
Wheel RPM = engine RPM/overall ratio; road speed = wheel RPM × tire circumference
4
Variables Explained
| Input | What it means |
|---|---|
| Engine RPM | Use the measured or stated value for this item, with the unit or category shown beside the field. |
| Drivetrain transmission ratio | Use the measured or stated value for this item, with the unit or category shown beside the field. |
| Tire diameter | Distance across a circle through its center; twice the radius. |
5
Worked Example
At 3,000 engine RPM and a 3:1 overall ratio, the wheel turns 1,000 times per minute.
6
Why Use This Calculator?
Use the formula and worked example to check the relationship between the input and output before carrying the result into a longer calculation.
7
Common Mistakes
- Include all applicable gear reductions; tire load and slip can change actual rolling distance.
8
Frequently Asked Questions
Should I round numbers before calculating?
Keep the original input precision through the calculation and round the final answer to the precision you need. Rounding an intermediate result can change later steps.
Why can a manual calculation differ slightly?
Check the operation, units, signs and rounding first. Equivalent fractions or expressions can look different while representing the same value.
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Sources & References
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