Why Propeller Size Matters
A propeller controls how an electric RC plane turns motor power into useful thrust. Diameter shapes the size of the air column. Pitch shapes how far the prop wants to move forward each revolution. Both values affect climb, speed, heat, noise, and flight time. A small pitch may climb well, yet it can limit top speed. A large diameter can pull strongly, yet it can overload the motor.
How This Estimator Helps
This calculator links aircraft weight, thrust target, motor speed, voltage, air density, blade count, and prop style. It then estimates a diameter from a thrust coefficient model. It also estimates pitch from the target pitch speed. The output gives rounded prop dimensions, static thrust, disk loading, current demand, power demand, and margin warnings. These results make early prop selection faster and safer.
Choosing Practical Inputs
Use real ready to fly weight when possible. Include battery, receiver, landing gear, camera gear, and payload. Select a thrust ratio that matches the model. Trainers often fly well near 0.6 to 0.8. Sport planes may need 0.9 to 1.2. 3D aircraft often need more than 1.5. Enter loaded RPM efficiency, not ideal no load speed. Most setups run below the simple Kv times voltage value.
Checking The Result
After the first estimate, compare the recommended prop with manufacturer current tests. Static current on the ground can be higher than current in flight. Leave margin for warm weather, aging batteries, and dense air. Ground clearance also matters. A safe diameter must avoid the runway, grass, and sudden nose dips.
Better Prop Testing
Use a watt meter before flying. Start with a slightly smaller pitch or diameter if the margin is tight. Run the motor briefly at full throttle. Check current, voltage sag, vibration, and temperature. Balance the prop and tighten the adapter correctly. A careful test protects the motor, speed controller, battery, and airframe.
Final Setup Notes
Propeller advice is an estimate. Different brands with the same label can draw different current. Thin electric props, slow fly props, and carbon props behave differently. Treat this page as a planning tool. The best size is the largest safe prop that stays inside electrical limits reliably.