RC Top Speed Calculator
Find the top speed of any electric RC car from motor KV, battery voltage, gearing, and tire size.
Free App
Pit Calc Pro
Have this calculator — and more racing calculators — right on your phone at the track.
Enter motor KV, voltage, and tire diameter to calculate speed
Gear ratio: 4.00:1 · FDR: 4.00:1
How to use this calculator
- • Enter your pinion and spur tooth counts to establish your gear ratio.
- • Search for your car to auto-fill the internal ratio and calculate the full final drive ratio (FDR).
- • Enter your motor's KV rating — found on the motor label or spec sheet.
- • Select your battery voltage from the quick-select chips, or type it in manually for LiHV or other chemistries.
- • Measure your rear tire outer diameter in millimeters and enter it above.
- • The speed grid shows how swapping pinion or spur gears changes top speed at your current KV, voltage, and tire size.
- • Click any cell in the grid to update your pinion and spur selection instantly.
- • Results are theoretical maximum speeds assuming 100% motor efficiency and no drivetrain losses.
- • Your settings are automatically saved for your next visit.
More RC Calculators
Free RC tools to dial in your car between rounds.
RC Gear Ratio Calculator
Pinion + spur + internal ratio → final drive ratio, rollout, and chart of nearby combos.
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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.
Free app
Pit Calc Pro
Have this calculator handy at the track
Pit Calc Pro puts this top speed calculator — and 6 more tools — right on your phone, so you're never without it when you need it most.
- Top speed calculator
- Gear ratio & FDR
- Pill insert geometry
- Corner weights
- Shock oil viscosity
- Fuel usage
