RPM Calculator
Estimate engine RPM from tire size, gearing and road speed.
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What this tool does
Estimate engine RPM from tire size, gearing and road speed. No torque-converter slip; nominal tire rolling circumference.
How to use the RPM Calculator
- Enter or select tire width (mm).
- Enter or select tire aspect ratio (%).
- Enter or select tire rim diameter (inches).
- Enter or select road speed (mph).
- Enter or select final drive ratio.
- Enter or select transmission ratio.
- Read the calculated result; change any measurement to compare alternatives.
Formula
engine RPM=mph×63360×axle×gear/(60×π×tire diameter)
- width
- Tire width (mm)
- aspect
- Tire aspect ratio (%)
- rim
- Tire rim diameter (inches)
- speed
- Road speed (mph)
- axle
- Final drive ratio
- gear
- Transmission ratio
No torque-converter slip; nominal tire rolling circumference.
Worked example
For rpm calculator, the following measurements illustrate the exact method: Tire width (mm): 225; Tire aspect ratio (%): 50; Tire rim diameter (inches): 17; Road speed (mph): 60; Final drive ratio: 3.73; Transmission ratio: 1.
Inputs
- Tire width (mm)225
- Tire aspect ratio (%)50
- Tire rim diameter (inches)17
- Road speed (mph)60
- Final drive ratio3.73
- Transmission ratio1
Result
- Engine RPM2,909.21
Results explained
- Engine RPM
- Engine RPM from the formula above. No torque-converter slip; nominal tire rolling circumference.
Frequently asked questions
engine RPM=mph×63360×axle×gear/(60×π×tire diameter)
Use the tire sidewall markings, actual vehicle specifications or recorded fuel/price values required by the inputs. Do not mix US gallons and imperial gallons.
No torque-converter slip; nominal tire rolling circumference.
Yes. Change the relevant size, price or efficiency while keeping the other inputs constant. Results update immediately.
No. Check manufacturer fitment, load and speed ratings, clearance and local requirements with a qualified technician.