Wind Turbine Power Calculator
The power a wind turbine produces from its rotor size and the wind speed — and why doubling the wind gives eight times the power.
The power in a column of moving air is ½ × air density × swept area × wind speed cubed.
How the wind turbine power calculator works
The power in a column of moving air is ½ × air density × swept area × wind speed cubed. No turbine can take all of it — the Betz limit is 59.3%, and real machines reach 35–45% — so the power coefficient is an input. Annual output uses a capacity factor, because the wind is not always at the speed you enter.
Formula: P = ½ · ρ · A · v³ · Cp; A = π · (D ÷ 2)²
Worked examples
| Inputs | Turbine output | Note |
|---|---|---|
| 100 m rotor at 10 m/s | 1,924 kW | 1,924 kW |
| 330 ft rotor at 22 mph | 1,852 kW | 1,882 kW |
| A 5 m home turbine in a 6 m/s breeze | 1 kW | 0.9 kW |
FAQFrequently asked questions
What is the Betz limit?
No turbine can capture more than 59.3% of the kinetic energy in the wind, because the air must keep moving to get out of the way. Real turbines reach 35–45% at their best wind speed.
Why is wind speed cubed?
Kinetic energy rises with speed squared and the mass of air arriving each second rises with speed, so power rises with the cube — twice the wind is eight times the power. Siting matters more than turbine size.
What wind speed should I enter?
The speed at hub height, not at ground level; wind is much stronger 80 m up. Use the annual mean with a capacity factor rather than a gusty day’s peak.
How do I use the capacity factor?
It converts the power at one wind speed into a year’s average output. Onshore wind farms typically achieve 25–40%, offshore 40–55%, and a small home turbine often under 20%.
Where these figures come from
- UK DESNZ / DEFRA — Greenhouse gas reporting: conversion factors — the flight, fuel and waste emission factors used here
- Scarborough et al. (2014), Climatic Change — Dietary greenhouse gas emissions — the per-diet daily emission figures
- US EPA — Technical Assistance Document for the Reporting of Daily Air Quality (AQI) — the PM2.5 breakpoints the air quality calculator uses
- UK Department for Energy Security and Net Zero — conversion factors — the official UK emission factors
Last checked: September 2026. Factors are taken from published government and peer-reviewed sources, each named on the page with its year.