RC Speed Calculator
A free RC car speed calculator — find the top speed of any electric RC car from motor KV, battery voltage, gearing, and tire size.
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.
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Free to start · iOS & Android
Setup App & Race Log
Got your top speed dialed? Track the whole setup.
The RC Setup App saves your settings for 600+ cars, has this gear calculator built in, and gives personalized AI tuning answers for your exact car — at the track or back in the pits.
- Gear Ratio Calculator
- AI Mechanic answers
- Setup Tracking
- Find & Share Setups
- Race Log
- Free to use
Just want the calculators?
Pit Calc Pro is our free standalone calculator app for iOS & Android.