🧮 RC Calculators & Tools
Every calc a racer, basher or pilot needs — gearing & rollout, top speed, LiPo runtime, motor RPM, corner/cross weight, power & ESC sizing, thrust and wing loading. Live, mobile, free, no signup. Change a number, get the answer instantly — real formulas shown.
⚙️ Gear Ratio & RolloutⓘHow far the car rolls forward for one full turn of the motor — the true measure of gearing.Rollout = (π × tire diameter) ÷ final drive ratio. Lets you compare gearing across different cars and tire sizes.More →
Final drive ratio and rollout (how far the car rolls per motor turn) — the number racers actually tune by.
FDR = (spur ÷ pinion) × internal · Rollout = π × tire ÷ FDR
Lower FDR = more top speed but hotter motor/ESC. Higher FDR = more punch & cooler. Internal ratio is printed in your chassis manual.
🏎️ Top Speed
Theoretical top speed from motor KV, battery, gearing and tire size.
mph = (KV × V × tire_in) ÷ (FDR × 336) · V = cells × 3.7
"Real" applies ~85% for efficiency, voltage sag and drag. Actual speed varies with traction, weight and tire growth.
🔋 LiPoⓘLithium-Polymer battery — the light, high-power rechargeable pack most modern RC uses.Each cell is 3.7V nominal, 4.2V full, ~3.8V storage. Handle with care: never over-discharge, over-charge, or run a puffed pack.More → Pack & Runtime
Pack voltages, energy, max safe current and runtime — plus a C-rating check.
Max A = (mAh ÷ 1000) × C · Runtime ≈ (Ah × 0.8 ÷ draw) × 60 · Wh = Ah × V
🌀 Motor KVⓘA brushless motor's RPM per volt with no load.A 3500Kv motor on a 2S (7.4V) pack spins ~25,900 rpm unloaded. Higher Kv = more top-end but more heat; lower Kv = more torque and cooler running.More → → RPM
No-load and loaded motor RPM from KV and pack voltage.
RPM = KV × V · V = cells × 3.7 · loaded ≈ × 0.8
KV = RPM per volt. Loaded uses ~80% for a typical geared load.
✈️ Prop Pitch Speed (planes)
Theoretical max airspeed a prop can deliver at a given RPM.
Pitch speed mph = pitch_in × RPM ÷ 1056
Real airspeed is ~85% of pitch speed after prop slip.
⚖️ Corner & Cross Weight
Balance your chassis: front/rear and left/right split, plus cross-weight — the number that makes a car turn equally both ways.
Cross % = (FR + RL) ÷ total × 100 · aim for ~50%
Cross weight near 50% means the car handles the same left and right. Off-50% tweaks it to favour one direction (oval/carpet).
⚡ Power & ESC Sizing
Watts your setup pulls, and the ESC current rating you should run with safe headroom.
W = V × A · V = cells × 3.7 · recommended ESC ≥ peak × 1.25
P = V × I is exact; the 25% headroom is a rule of thumb so the ESC runs cool. Match connectors/wire gauge to the current too.
🚀 Thrust-to-Weight (air)
Static thrust vs all-up weight — how hard your plane or drone will pull.
T:W = thrust ÷ weight
~0.5 = gentle trainer · ~1 = sporty · 1.5+ = aerobatic · 2+ = unlimited vertical / 3D & racing drones.
🪽 Wing Loading (planes)
Weight spread over wing area — lower flies slower and more forgiving, higher flies faster and sinkier.
Loading = weight ÷ wing area · oz/ft² = g/dm² × 0.3277
Trainers/park flyers ~30–50 g/dm². Warbirds & jets run much higher and need more speed to fly.
Real formulas, no signup — change a number, get the answer. Join the crew to save your rigs and get AI setup help tuned to your exact build.