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Formula & Calculator

Propeller Efficiency

Ratio of useful propulsive (thrust) power output to shaft power input for a propeller.

Written by the Vorzep Team

PropulsionAircraft PerformanceEfficiency

Propeller Efficiency Calculator

ηp = T · V / Pshaft
Select the variable to solve for, then enter the other three values
ηpTVPshaft
Solve for:
Aircraft Presets
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Unit System
System:
Enter the other three values
—
N
m/s
W
ηp = propeller efficiency (0.7–0.9 typical) Pshaft = power delivered to propeller T · V = useful power (thrust × velocity)
η_p = T * V / P_shaft
Propeller Efficiency

Variables

SymbolQuantityUnit
η_pPropeller efficiency
TThrustN
VAirspeedm/s
P_shaftShaft powerW

What it means

Propeller efficiency is a measure of the effectiveness of a propeller in converting engine shaft power into useful thrust power. It depends on the advance ratio (J = V/(nD)) and the propeller design. At design speed, η_p is typically 0.8‑0.9. It is used in performance analysis to determine power available and to calculate the propulsive efficiency. Understanding propeller efficiency is essential for optimising propeller design and for matching the engine to the propeller.

Worked example

Propeller Efficiency – Two Examples

Real‑World
Scenario: T = 3000 N, V = 60 m/s, P_shaft = 220,000 W. Find η_p.
ParameterValue
T3000 N
V60 m/s
P_shaft220,000 W
1η_p = T×V/P_shaft = 3000×60/220000 = 180000/220000 = 0.818 (81.8%)
Result 0.818 ✓ Good
Scenario: T = 4000, V = 80, P_shaft = 320,000. Find η_p.
ParameterValue
T4000
V80
P_shaft320,000
1η_p = 4000×80/320000 = 320000/320000 = 1.0 (100% – ideal)
Result 1.00 ✓ Ideal
Key insight: Propeller efficiency = thrust power / shaft power – typical values 0.7–0.85.

Common mistakes

  • Propeller efficiency: η_p = T·V / P_shaft.
  • T: Thrust (N).
  • V: Forward speed (m/s).
  • P_shaft: Input power (W).
  • Typically 0.7‑0.85 for cruise.

Applications

Propeller efficiency, η_p = T·V / P_shaft, is the ratio of useful thrust power to shaft power. It quantifies how effectively the propeller converts engine power into thrust. Efficiency depends on advance ratio and blade pitch. Engineers use this to select propellers, to design pitch control systems, and to assess overall propulsion efficiency. By maximising η_p, aerospace engineers can improve the performance of light aircraft, UAVs, and turboprops, reducing fuel consumption and extending range.

  • Propeller selection and performance mapping
  • Design of constant‑speed and variable‑pitch propellers
  • Engine‑propeller integration and testing
  • Performance analysis of turboprop and piston aircraft
  • Propeller design optimisation for specific missions