Wind Turbine Tip Speed Ratio (TSR) Calculator

Tip speed ratio (TSR, written λ) compares how fast a blade's tip moves through the air to how fast the wind itself is moving: λ = (ω × R) ÷ V, where ω is the rotor's angular velocity in radians per second (RPM × 2π ÷ 60), R is the blade radius, and V is the wind speed. It's a plain ratio, so it comes out identical whether every input is measured in metric or imperial units, as long as they're converted consistently.

This is a different question from this site's Wind Turbine Power Output calculator, which answers how much power a turbine extracts from the wind. TSR instead answers how fast the blades are spinning relative to the wind passing over them — the number a blade's airfoil shape is actually designed around. Run the rotor too slowly for the wind speed and much of the wind's energy slips past the blades untouched; run it too fast and the blades act more like a spinning wall, generating drag and turbulence instead of lift.

That tradeoff is why turbine designs cluster at very different TSRs: slow, high-torque multi-blade rotors (like a traditional farm windmill) are built to run at a low tip speed ratio, while the slender two- and three-blade rotors on modern utility-scale turbines are designed to run at a considerably higher one — a general trend confirmed across the published literature, even though the exact optimal number varies by blade count, airfoil profile, and design method, so this calculator reports the ratio itself rather than grading it against a single numeric band.