RC Gear Ratio Calculator
Compare setups side by side and find the ideal pinion/spur combination.
Change Impact Chart
% change vs. your current setup. Click any cell to set it as the new setup.
| Spur ↓ Pinion → | 16T | 17T | 18T | 19T | 20T | 21T | 22T | 23T | 24T |
|---|---|---|---|---|---|---|---|---|---|
| 76T | |||||||||
| 77T | |||||||||
| 78T | |||||||||
| 79T | |||||||||
| 80T | |||||||||
| 81T | |||||||||
| 82T | |||||||||
| 83T | |||||||||
| 84T |
Change
0.0%
No change
Current
Gear Ratio
4.00:1
New
Gear Ratio
4.00:1
Free App
Pit Calc Pro
Have this calculator — and more racing calculators — right on your phone at the track.
How to use this calculator
- • Enter your current pinion and spur tooth counts to establish a baseline.
- • Enter a new setup to compare, or click any cell in the chart to set it as the new setup.
- • Search for your car model to auto-fill the internal ratio.
- • Add rear tire diameter to calculate rollout — the distance traveled per motor revolution.
- • Positive change = higher ratio = more torque and acceleration.
- • Negative change = lower ratio = higher top speed, but more strain on the motor.
- • Want the actual mph? The RC speed calculator turns your gearing, motor KV, and voltage into a top-speed number.
- • Your settings are automatically saved for your next visit.
More RC Calculators
Free RC tools to dial in your car between rounds.
RC Speed Calculator
Motor KV, battery voltage, gearing, and tire size → top speed of any electric RC car.
RC Gear Ratio & Rollout Chart
Pinion/spur chart for any class — gear ratio (FDR) or rollout (mm). 1/10, 1/12 pan, 1/8 presets included.
RC Corner Weight Calculator
Enter per-wheel weights to compute cross weight and balance — critical for oval and on-road tuning.
RC Shock Oil Weight Converter
Convert wt ↔ cSt ↔ Mugen / Yokomo numbers, plus starting-point oil weights by class.
RC Battery Runtime Calculator
How long will your LiPo last? Estimate runtime by class and driving style.
RC Pill Insert Calculator
Diff insert geometry for 1/8 buggies — match your gear-diff pill setup to your conditions.
Mini-Z Wheel Offset Calculator
Fitting an AutoScale body to a Kyosho Mini-Z? Get the exact wheel offset for any width, plus a wheelbase & motor-mount reference.
Free app
Pit Calc Pro
Have this calculator handy at the track
Pit Calc Pro puts this gear calculator — and 6 more tools — right on your phone, so you're never without it when you need it most.
- Speed calculator
- Pill insert geometry
- Corner weights
- Shock oil viscosity
- Fuel usage
- Oil blending
