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Calcimator

Aerodynamic Drag (CdA) Calculator

Estimate your CdA (drag area) from speed and power data. See how aerodynamic and rolling resistance forces split at different speeds.

Inputs

mph
W
lb
kg/m³

Results

CdA (Drag Area)

0.3886 m²

≈ 6 sheets of paper

Aerodynamic Drag Force22.5 N
Rolling Resistance Force3.22 N
Power to Overcome Aero Drag219 W
Power to Overcome Rolling31 W
Aero as % of Total Resistance87.5%
How to Use This Calculator
  1. Enter your Speed in km/h and Power Output in watts.
  2. Set Total Weight (rider plus bike in kg) and Air Density (use 1.225 kg/m³ at sea level).
  3. Adjust Rolling Resistance (Crr) to match your tires for your setup.
  4. Review the calculated CdA (drag area), Aerodynamic Drag Force, Rolling Resistance Force, and the wattage cost of each.
  5. Use Aero as % of Total Resistance to prioritize equipment upgrades.

How the result changes with Speed

SpeedCdA (Drag Area)
155.34 m²
280.7807 m²
430.2027 m²
550.092 m²

What each input means

Speed
Steady-state speed on flat ground with no wind. Use a GPS-verified segment.
Power Output
Average power output at the given speed, recorded by a power meter.
Total Weight (rider + bike)
Combined weight of rider and bicycle.
Air Density
Air density at your location. Sea level at 15°C = 1.225. Higher altitude = lower density.
Rolling Resistance (Crr)
Tire rolling resistance coefficient. Fast road tire: 0.003-0.004, gravel: 0.006-0.008.

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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