Wind Turbine Blade Length Calculator
Calculate wind turbine blade length, rotor diameter, swept area and expected output from wind speed, Cp and efficiency — or estimate the required blade size for a target power.
🌬️ Field Rule: For a normal horizontal-axis turbine, blade length is approximately the rotor radius. If blade length doubles, swept area becomes four times larger. Use this with the Swept Area Calculator, Wind Turbine Power Calculator, Tip Speed Ratio Calculator, RPM Calculator and Efficiency / Cp Calculator.
🪶 Blade Length → Swept Area → Wind Power
Blade Length / Radius
Average Wind Speed
Air Density
Power Coefficient Cp
Electrical Efficiency
Blade Count Optional
Blade count does not change swept area directly. Blade length/radius controls the circular swept area.
Presets:0.5m micro1m small1.5m home2.5m rural5m farm20m large
Target Electrical Power
Design Wind Speed
Air Density
Expected Cp
Electrical Efficiency
Design Oversize
Reverse sizing estimates the blade radius needed for a selected power at a selected wind speed. Real machines also need structural, RPM and generator checks.
Targets:100W500W1kW3kW5kW10kW
Target TSR
Rotor RPM
Wind Speed
Air Density
Cp Optional
Electrical Efficiency
Use this when you have a desired tip speed ratio and rotor RPM. Formula: blade length = TSR × wind speed ÷ angular speed.
TSR presets:slow rotormulti-blade3-bladefast rotor
📐 Formula Reference
Blade Length / Radius
blade length ≈ radius = D ÷ 2
Swept Area
A = π × blade length²
Wind Power
Pwind = 0.5 × ρ × A × v³
TSR Based Length
radius = TSR × wind speed ÷ angular speed
📋 Quick Reference
Blade Length vs Diameter
0.5 m blade1 m rotor
1.5 m blade3 m rotor
5 m blade10 m rotor
Area Growth
1 m blade3.14 m²
2 m blade12.57 m²
3 m blade28.27 m²
Planning Notes
Blade lengthradius
Diameter2 × radius
Power effectarea × v³
📚 Engineering Notes
Longer blades collect more windBlade length increases swept area by the square of radius. A small increase in blade length can significantly increase available wind power.
Blade length alone is not enoughThe final turbine design also depends on TSR, blade profile, generator matching, tower height, cut-in wind speed and structural strength.
Wind speed matters more than most people expectWind power changes with the cube of wind speed. The same blade length performs very differently at 5 m/s and 8 m/s.
Use target sizing conservativelyTarget power sizing assumes steady wind. Real annual energy needs capacity factor and local wind distribution.
What is a Wind Turbine Blade Length Calculator?
A wind turbine blade length calculator estimates blade radius, rotor diameter, swept area and possible power output. For a horizontal-axis turbine, blade length is usually treated as the radius from the hub center to the blade tip.
How blade length affects wind turbine power
Wind turbine power is proportional to swept area, and swept area is proportional to blade length squared. This means doubling blade length gives about four times the swept area before considering wind speed, Cp and electrical efficiency.
Blade length vs rotor diameter
Blade length is approximately the rotor radius. Rotor diameter is twice the blade length. A 1.5m blade gives roughly a 3m rotor diameter, while a 5m blade gives roughly a 10m rotor diameter.
Important limitation
This calculator gives engineering estimates. Actual blade design requires aerodynamic profile, TSR, chord, twist, material strength, hub design, generator matching, overspeed protection and local wind conditions.
❓ Frequently Asked Questions
For a horizontal-axis turbine, blade length is approximately rotor radius. If target power is known, calculate required swept area from P = 0.5 × ρ × A × v³ × Cp × efficiency, then calculate blade length as sqrt(area ÷ π).
Usually yes for basic calculations. Blade length is commonly taken as the distance from hub center to blade tip, which is the rotor radius. Rotor diameter is twice the blade length.
It depends heavily on wind speed and turbine efficiency. At around 8 m/s with moderate Cp and electrical efficiency, a 1 kW output may require a blade length around 1.4 to 1.8 meters. At lower wind speed, the blade must be much longer.
A rough 5 kW turbine at good wind speed may use blades of a few meters long, but exact size depends on wind speed, Cp, generator efficiency and rated design. Use the target power tab for a quick estimate.
Longer blades increase swept area and available wind power, but the turbine also needs the right generator, controller, tower, blade strength and overspeed protection. Oversized blades can overload the generator or structure.
Because swept area is πr². If the radius/blade length doubles, the swept area becomes four times larger. Wind speed still has an even stronger cube relationship with power.
Yes. Blade length equals TSR × wind speed divided by angular speed. This helps match rotor size, RPM and target tip speed ratio.
More blades can change starting torque and optimum TSR, but they do not directly change swept area. Swept area is mainly controlled by blade length or rotor radius.