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Power to Weight Ratio Converter

Aircraft Power-to-Weight Ratio

Calculate shaft power P/W for piston and propeller aircraft. See the note below for jet aircraft.

Decimals:
3
Note for jet aircraft: Jet and turbofan engines are rated in thrust (Newtons or lbf), not shaft power (kW or hp). For those aircraft, the relevant metric is the dimensionless thrust-to-weight ratio (T/W). The calculator below applies to piston-engine and turboprop aircraft where shaft power is the relevant figure.
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Power-to-Weight vs Thrust-to-Weight in Aviation

The term "power-to-weight ratio" in aviation means different things depending on the aircraft type:

  • Piston and turboprop aircraft — the engine produces shaft power (measured in kW or hp), driving a propeller. P/W in kW/kg or hp/lb is a useful performance metric for these aircraft.
  • Jet and turbofan aircraft — the engine produces thrust directly (measured in kN or lbf). The relevant figure is thrust-to-weight ratio (T/W), which is dimensionless. For fighter jets, T/W > 1.0 means the aircraft can accelerate vertically.

This calculator uses shaft power, making it most useful for general aviation piston aircraft, aerobatic planes, and turboprop regional aircraft.

Worked Examples

  • Cessna 172 Skyhawk: 134 kW / 1,111 kg MTOW = 0.121 kW/kg — typical light GA aircraft.
  • Piper PA-28 Cherokee: 112 kW / 1,089 kg = 0.103 kW/kg
  • Cirrus SR22: 231 kW / 1,633 kg = 0.141 kW/kg — high-performance single.
  • Beechcraft King Air C90B (turboprop): 2 × 410 kW / 4,581 kg = 0.179 kW/kg
  • Pitts Special S-1 (aerobatic): 134 kW / 358 kg = 0.374 kW/kg — exceptional aerobatic performance.

FAQs

Why don't jets use power-to-weight ratio?
Jet engines produce thrust directly — they accelerate exhaust gas rearward to generate force. Shaft power (kW) isn't a useful measure for this. Thrust-to-weight (T/W) is the standard: a T/W above 1.0 means the engine can lift the aircraft vertically, which is the threshold for fighter jet maneuverability.
Should I use empty weight, useful load, or MTOW?
For comparing aircraft performance, use Maximum Takeoff Weight (MTOW). This is the worst-case scenario and the most consistent basis for comparison. Some pilots use empty weight + pilot to estimate performance at their typical operating weight.
What is a good power-to-weight ratio for a light aircraft?
For general aviation piston aircraft, 0.10–0.15 kW/kg (at MTOW) is typical. Aerobatic aircraft aim for 0.25 kW/kg or more for snap rolls and vertical figures. Sport and ultralight aircraft vary widely depending on design goals.

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