Estimate static thrust, induced velocity and tip speed from shaft power and diameter using simplified momentum theory.
Estimate static thrust, induced velocity and tip speed from shaft power and diameter using simplified momentum theory. Simplified momentum-theory estimate, not a manufacturer performance chart.
Static thrust estimate (N)
How to use this tool
Power delivered to the propeller in kilowatts.
Diameter in metres and rotational speed in revolutions per minute.
1.225 kg/m³ at sea level; lower at altitude.
Thrust is a static (zero forward speed) estimate; tip Mach warns about compressibility losses.
Formula & worked example
Power 100 kW, diameter 2 m, 2,400 RPM, sea-level air: disc area 3.1416 m², induced velocity 23.51 m/s, static thrust ≈ 4,254 N, tip speed 251.33 m/s (Mach 0.733).
Limitations — read this before you rely on it
This is a simplified momentum-theory estimate for static thrust only — it is not a manufacturer performance chart. It ignores blade geometry, pitch, tip losses, forward speed and compressibility effects, so treat thrust as an order-of-magnitude estimate for design comparison, not a certified figure.
Frequently asked questions
Real thrust depends on blade airfoil, pitch distribution and tip losses that momentum theory averages away.
Thrust falls as forward speed rises because the inflow velocity through the disc increases.
Above about Mach 0.8–0.9 the blade tips lose efficiency and become very noisy due to shock formation.
Yes for static thrust — a larger disc accelerates more air more slowly, which is more efficient for the same power.
The same theory applies at small scale, but low Reynolds numbers and small-blade effects make drone results rougher.