Energy & Environment

Wind Turbine Power Calculator

Enter rotor size and wind speed to estimate the power a wind turbine produces.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

Rotor diameter

Wind speed

Power coefficient Cp

Small turbines often 0.25 to 0.4; the theoretical maximum (Betz limit) is 0.593

Air density (kg/m³)

Capacity factor for yearly energy

Rated power (W), optional cap

Your results

Power output (W)

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Power in the wind (W)

—

Swept area (m²)

—

Yearly energy at the capacity factor (kWh)

—

Betz limit power (W)

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Wind Turbine Power Calculator by TheCalcTools

How the Wind Turbine Power Calculator works

The power in the wind passing through the rotor is ½ ρ A v³, so doubling the wind speed gives eight times the power. A turbine captures a fraction Cp of it, at most 16/27 (59.3%), the Betz limit.

Yearly energy depends on how the wind varies. The capacity factor (the average output as a share of rated power) captures this; small turbines on houses often achieve under 20%.

The formula

P = ½ × ρ × A × v³ × Cp, A = π d² ÷ 4

Worked example

Using the default values shown in the calculator:

Rotor diameter	3
Wind speed	6
Power coefficient Cp	0.35
Air density (kg/m³)	1.225
Capacity factor for yearly energy	20 %
Rated power (W), optional cap	0

A 3 m rotor sweeps 7.07 m². At 6 m/s the wind carries 935 W.
With Cp 0.35 the turbine makes 327 W.

Result:

Power output (W)	327
Power in the wind (W)	935
Swept area (m²)	7.07
Yearly energy at the capacity factor (kWh)	573
Betz limit power (W)	554

Frequently asked questions

Why do turbines need tall towers?

Wind is faster and steadier higher up, and power rises with the cube of speed.

Sources and further reading

More in Energy & Environment · All calculators

This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.