Cycling Power in Watts
Estimates cycling watts from rider weight, speed and grade.
—
Cycling power: watts, FTP and W/kg
Cycling power measures the mechanical work you produce at the pedals: P = F · v = T · ω. That is force times speed at the wheel, or torque times angular velocity at the crank, and either way the answer comes out in watts. Going uphill, gravity does most of the work: P_grav ≈ m · g · v · sin(slope). Example: a 75 kg rider at 25 km/h on a 2% grade needs roughly 200-220 W once you add in aero and rolling resistance. The FTP (Functional Threshold Power) is the highest power you can hold for about an hour. The Coggan protocol estimates it as ≈ 95% × the average power of a 20-minute all-out test. The W/kg ratio levels the field across body sizes: Tadej Pogacar holds around 6.4 W/kg on 30-minute climbs, while a recreational rider sits closer to 2.5-3 W/kg.
Applications: training, racing and indoor cycling
Power data is what runs indoor sessions on Zwift, TrainerRoad and Rouvy, where a smart trainer reads your watts in real time. Wahoo Elemnt and Garmin Edge head units show power zones (Coggan Z1-Z7) and keep track of TSS/IF for periodization. Strava normalizes its segment leaderboards by W/kg, while Bkool and Sufferfest build workouts around %FTP. A typical plan puts intervals at 88-94% FTP for sweet spot, 95-105% for threshold, and 106-120% for VO2max.
FAQ
Do I need a power meter to use this? A power meter (Stages, Quarq, Favero) or a smart trainer gives you the real number. Without one, you can still estimate from speed, grade and weight, just keep in mind that wind and road surface throw the figure off.
Why 95% of the 20-min test? Coggan's data showed that athletes can hold roughly 95% of their 20-minute power across a full hour. Some riders prefer the ramp test, or the newer lab-style protocols from Karoo/INSCYD.
How often should I retest FTP? Roughly every 6-8 weeks while you are training in a structured block. When the numbers stop moving, that is the signal to reset your zones.
Is W/kg the only metric that matters? Not really. On flat time trials, raw watts and aerodynamics decide the result. W/kg only takes over on the long climbs.
Related Tools
Resistor Power Dissipation Calculator (Watts)
Computes the power dissipated in a resistor in watts from current and resistance or from voltage and resistance.
Bearing Power Loss
Calculate the power dissipated by friction in a bearing, P = T × ω, multiplying the friction torque T by the angular velocity ω (rad/s). The result, in watts, is the mechanical energy converted to heat per unit time by friction — a loss that reduces efficiency and heats the lubricant and components. This heat must be dissipated (by convection or oil circulation) to keep a safe operating temperature, since overheating degrades the lubricant and can cause seizure. Estimating the dissipated power is essential to size the cooling and the oil flow. Enter the friction torque and the angular velocity.
Inductor Current Ripple
Calculate the inductor current ripple of a buck converter, ΔI_L = (V_in × D) ÷ (L × f), from the input voltage V_in, the duty cycle D, the inductance L and the switching frequency f. The result, in amperes, is the peak-to-peak variation of the inductor current each cycle. It is a central design parameter: a typical ripple of 20-40% of the average current is a good compromise. Higher inductance and frequency reduce the ripple (larger inductor, more costly; higher frequency, more switching losses). It also sets the boundary between continuous and discontinuous conduction. Enter the voltage, duty cycle, inductance and frequency.
Wave Power
Estimate the power flux of an ocean wave per meter of wave front, P ≈ 0.5 × H² × T, from the wave height H (m) and the period T (s), in deep water (seawater). The result, in kW/m, is the power available per meter of wave front width — a key indicator of wave energy potential for converters (WECs). Coasts exposed to ocean swells (European Atlantic, Pacific) reach 30-70 kW/m, a significant renewable resource. The power grows with the square of the height and linearly with the period. Enter the wave height and period.
Cycling Cadence to Speed Calculator
Computes cycling speed from cadence (rpm), chainring, cassette teeth and wheel diameter.
Power by Admiralty Coefficient
Estimate a ship's propulsive power by the Admiralty formula, P = (∆^(2/3)·V³)/C, from the displacement (∆, t), the speed (V, knots) and the Admiralty coefficient (C), characteristic of similar hulls. It is a classic, fast method to predict the required power in the preliminary design stage, based on similarity with existing ships. The V³ dependence shows the high cost of speed. Enter the displacement, the speed and the coefficient C.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.