ESC Rating Calculator
Calculate ESC amperage rating needed from motor specs and propeller load. Size electronic speed controllers for drone and RC builds safely.
Specialist tool for RC Drones1 documented formula12 real workflowsPrivate in your browser
Use this result well
A quick decision brief for this specific tool
Inputs that matter
Motor Max Current, Number of Motors, Safety Margin, Burst Duration
Output to expect
ESC Rating Calculator
How it works
1 documented formula across 1 calculation mode
- Keep 4 bounded inputs within the limits shown beside the fields.
- Confirm that every value uses the unit and time basis shown before comparing scenarios.
- Change one input at a time to see which assumption materially changes the result.
Was this tool helpful?
Related Tools
Tools you might need next
Defensive Rating
Estimate team defensive rating from opponent box score. Free online basketball calculator with instant, accurate results.
Basketball
Bearing ABEC Rating Speed
Compare bearing ABEC ratings and estimated roll speed. Free online skateboarding calculator with instant, accurate results.
Skateboarding
Course Rating vs Slope Calculator
Convert Handicap Index to Course Handicap using rating and slope. Free online golf calculator with instant, accurate results.
Golf
Reference & details
How it works
Updated July 2026
How it works
Updated July 2026Motor Max Current
Motor specs list max continuous and burst current at recommended prop/voltage. Bench tests with watt meter at full throttle give actual loaded current.
ESC continuous rating ≥ motor max continuous current × 1.2 marginProp and Voltage Load
Larger props and higher cell count increase current at the same throttle. Current scales roughly with voltage and prop load torque.
I ∝ V × prop load torque (empirical — measure on thrust stand)Burst vs Continuous Rating
ESC burst rating (10–30 s) handles punch-outs; continuous rating must cover sustained hover and cruise. Size for continuous, verify burst for acro.
ESC burst ≥ peak current × 1.1; ESC continuous ≥ avg high-throttle currentUpdated: July 2026
Example Scenarios
Motor max 35A continuous, 45A burst on 5×4.3 prop. ESC: 35A continuous minimum, 45A+ burst. Most builders use 40–50A ESC for headroom.
Cruise at 12A, peak 28A on 2806.5 motor. 30A continuous ESC sufficient; 40A provides margin for wind gusts without 60A overweight ESC.
Motor draws 38A max on 10×6 prop. 40A ESC meets spec; 50A adds cooling margin for summer flights with poor airflow in fuselage mount.
Common Mistakes to Avoid
Common Mistakes to Avoid
Sizing ESC from battery C-rating instead of motor draw
A 100C 1500 mAh battery can theoretically deliver 150A, but motor-prop combo determines actual draw. Size ESC to motor load, not battery capability.
Ignoring ESC mounting airflow
An ESC rated 40A needs airflow in flight. Enclosed mounts without cooling effectively reduce rating — add heatsink or choose higher-rated ESC.
FAQ
20–30% above measured max continuous current. For a 30A motor, use 40A ESC. Burst rating should exceed recorded peak amp draw from blackbox logs.
Yes. 4-in-1 boards rate total or per-motor current — verify per-motor rating matches individual motor draw. Heat dissipation is concentrated on one board.
Protocol (DShot, PWM) affects response time, not thermal rating. Physical MOSFET size, PCB copper, and heat sinking determine amp capacity.
Thermal shutdown mid-flight, desync, or permanent MOSFET failure. Smoke and crash typically follow sustained over-current beyond ESC rating.
Rating is hardware-dependent, not firmware. Same amp rating ESCs perform similarly; 32-bit ESCs offer better filtering and telemetry, not higher amp capacity.
About ESC Rating Calculator
Undersized ESCs overheat and fail; oversized ESCs add unnecessary weight. This calculator determines required ESC continuous and burst current rating from motor max current, prop load, and battery voltage.