How do I calculate RC car speed?
Motor KV and battery voltage estimate motor RPM. Final drive ratio reduces that speed at the wheels, and tire circumference converts wheel RPM into vehicle speed.
Live tool / drivetrain math
RC Speed & Rollout Calculator
Estimate RC speed, wheel RPM, and rollout from your gearing, tire diameter, motor KV, and pack voltage.
Read the result
A useful estimate, not a speed promise.
How it calculates
Motor KV × nominal voltage estimates motor RPM. Final drive ratio reduces that to wheel RPM, while tire circumference turns wheel RPM into distance.
What changes real speed
Battery sag, tire growth, gearing, terrain, aero, traction, and vehicle load all change real-world speed. Confirm specs and test safely.
Setup reference
What this calculator does
Combine gearing, tire diameter, motor KV, and battery voltage to estimate no-load and loaded RC speed. Use the result to compare setup directions before chasing a higher top speed.
FAQ
RC setup questions
Why is loaded RC speed lower than no-load speed?
No-load speed ignores vehicle mass, tire drag, aero load, drivetrain losses, and voltage sag. A loaded estimate applies an efficiency assumption.
Does a larger tire make an RC car faster?
A larger tire travels farther per wheel revolution, which increases rollout and theoretical speed while also increasing drivetrain load.