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Aerodynamics & Power

Estimate your aerodynamic drag, then explore what a change in CdA could mean for your performance.

Bike style

Sets the initial rolling resistance and drivetrain efficiency. Both can be changed in Advanced Settings.

Calculate

Estimate your CdA from average power and speed.

Estimated CdA
—m²

Your estimated aerodynamic drag becomes your baseline below.

Explore an aerodynamic change

Adjust CdA up or down relative to your baseline and compare the effect on performance.

Baseline CdA—m²
Modified CdA—m²
Steps of 0.001 m²

Reduced aerodynamic drag

Performance difference

At the same speed— —Compared with baseline
At the same power— —Compared with baseline

Estimated time difference

Estimated time saved — At the same power

The power saving and speed increase are two alternative scenarios, not gains that occur simultaneously. Time estimates assume constant power and steady-state speed.

Power vs speed

Compare the power required around your calculated speed. The red curve is your modified CdA.

Power required at different speeds Grey baseline and red modified CdA power curves. Exact comparison values are provided above.

Focused view around your calculated speed. The power axis is zoomed and may not start at zero.

Advanced SettingsCrr 0.0025 · Efficiency 97% · Air density 1.225 kg/m³

Resistance from your tyres and the riding surface. Lower Crr means less power is needed at the same speed.

Use the arrows to adjust in steps of 0.0001.
Illustrative starting points
Optimised indoor track0.0020
General indoor track0.0025
Fast road racing tyres0.0030
General performance road0.0040
Actual values depend on tyre, pressure, load and surface.

The share of crank power delivered to the wheel after drivetrain losses. A clean, well-maintained road drivetrain may exceed this road preset.

Example at 500 W crank power
95% efficiency25 W lost
97% efficiency15 W lost
98% efficiency10 W lost
Efficiency varies with chain condition, lubrication, gearing and load.

Denser air produces more aerodynamic drag at the same speed and CdA. If available, enter measured air density from your test conditions.

Use the arrows to adjust in steps of 0.001 kg/m³.
Approximate examples
Standard atmosphere, 15°C, sea level1.225
Warm indoor velodrome, approx. 26°C1.18
Temperature, pressure, elevation and humidity all affect density.