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Prop thrust calculator

Enter the prop size and RPM - or your motor's Kv and battery voltage - to estimate thrust. Add the model's weight for its thrust-to-weight ratio.

A 10x5 prop is 10 in diameter, 5 in pitch.
Leave empty to estimate from Kv × volts (85% of that, under load).
3.7 V a cell: 3S = 11.1 V, 4S = 14.8 V, 6S = 22.2 V.
0 for static thrust on the bench.

Result

Fill in the numbers above to see the result.

How it works

We use a published empirical formula for typical sport props (Gabriel Staples, 2013): thrust (N) = 4.392399×10⁻⁸ × RPM × D^3.5 ÷ √P × (4.23333×10⁻⁴ × RPM × P − airspeed in m/s), with D and P in inches.

Pitch speed is how fast the prop would screw through the air with no slip: RPM × pitch. The model's top speed is usually a little below it.

Under load a motor turns at roughly 85% of Kv × volts. Treat the result as a guide - prop shape, motor and battery all change it, so a thrust stand or wattmeter has the final word.

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