The advanced cycling power calculator: calculate the power required to ride at a given speed, or estimate the speed you can hold at a given power — with full control over gradient, wind, aerodynamics, rolling resistance and drivetrain efficiency.
Estimated cycling power based on the inputs provided. Real-world power can differ because of equipment, road surface, wind variability and rider position.
Cycling power is the rate at which you do mechanical work to move your bike forward, measured in watts. Unlike speed, power isn't affected by wind or gradient changing your pace — it directly reflects how hard you're working, which is why power meters have become the standard tool for structured training and pacing.
At a constant speed, the power at your pedals equals the power needed to overcome three physical forces, divided by how efficiently your drivetrain transmits that power:
Take a 165 lb rider on an 18 lb bike, riding on the hoods with standard wheels and race tires, on flat ground with no wind:
That works out to 2.31 W/kg for this rider. Enter these same numbers into the calculator above to see the full breakdown, or change any input to see how it shifts the result.
Rider and bike weight matter most on climbs, where gravity dominates. Speed, riding position and wheel choice matter most on flat or rolling terrain, where aerodynamic drag dominates. Tire choice and pressure affect rolling resistance on every surface, and chain lubrication and derailleur pulley bearings each cost a small, steady percentage of your power regardless of terrain.
Watts alone don't tell you how hard an effort feels relative to your body — a heavier rider needs more absolute watts to match a lighter rider's climbing speed. Dividing power by body weight gives watts per kilogram (W/kg), the standard way to compare climbing performance across riders of different sizes. See the W/kg Calculator to calculate and classify your own ratio.
Functional Threshold Power (FTP) is an estimate of the highest power you can sustain in a quasi-steady state without rapidly fatiguing, often associated with roughly an hour of effort — it's the reference point most structured training plans use to set intensity zones. The watts this calculator produces are a snapshot for one set of conditions; FTP is a fitness benchmark you build training zones around. Use the FTP Calculator to estimate yours from a field test.
On a sustained climb, gravity dominates total power far more than it does on flat ground, so the same power output produces a much slower speed as gradient increases. The Hill Climb Calculator uses this same model to estimate climbing time and VAM (vertical ascent per hour) from your power output.
Speed and power aren't linearly related — because aerodynamic drag grows with the square of speed, going faster costs disproportionately more watts the faster you already are. Use the Speed Calculator to explore that relationship directly.
CdA (drag coefficient × frontal area) is the single input that drives the drag term in this calculator's advanced mode. If you have a measured power and speed from a real ride but don't know your own CdA, the CdA Calculator estimates it for you — plug that number back into the drag section above for a more accurate result than the position-based defaults. To see the aerodynamic-drag or rolling-resistance component on its own, without the full breakdown, use the Aero Watts Calculator or the Rolling Resistance Calculator.
