Cycling Wattage Calculator

Cycling power overcomes rolling resistance, gravity (on hills) and air drag.

How the Math Works

The Cycling Wattage Calculator uses the fundamental physics equation P = (F_roll + F_grav + F_aero) × v to determine the power required to maintain a specific speed. This formula accounts for three primary forces: rolling resistance (F_roll), which resists tire motion on the road surface; gravitational resistance (F_grav), which must be overcome when climbing hills; and aerodynamic drag (F_aero), which increases exponentially with speed. Each force component is calculated separately then summed to find total resistance, which is finally multiplied by velocity (v) to yield power in watts - the rate of energy expenditure needed to sustain the target speed.

Practical Applications

To use this calculator practically, first input your desired speed in miles per hour or kilometers per hour, along with your bike's weight and your body weight combined. Next, enter the road grade percentage (0 for flat terrain, positive for uphill, negative for downhill) and your rider drag coefficient, which typically ranges from 0.3 to 0.5 for upright positions. The calculator will output the exact wattage needed, allowing you to plan training zones, set realistic power goals for races, or determine if your current fitness level can achieve target speeds on specific routes.

Day-to-Day Use

Understanding your power requirements transforms cycling from guesswork into data-driven training. Before heading out, you can check if your planned route is achievable given your current fitness level, preventing frustrating attempts at speeds beyond your capabilities. During group rides, you'll know precisely how much effort each segment demands, helping you pace yourself effectively. Whether you're preparing for a charity century, commuting to work, or planning a mountain climb, this knowledge helps optimize nutrition timing, gear selection, and recovery strategies to make every ride more efficient and enjoyable.

Worked example

80 kg at 30 km/h on the flat → about 165 W.

FAQ