Cycling Wattage Calculator
Estimate the pedal power needed to hold a steady speed after accounting for climbing, rolling resistance, aerodynamic drag, and drivetrain losses.
Ride assumptions
Switching units converts the current values rather than relabeling them.
Body mass including normal riding clothing.
Include bottles, bags, tools, and carried equipment.
Steady ground speed, not a short peak or sprint value.
Sets the frontal-area drag estimate (CdA).
Combines with Surface to set rolling resistance.
Adds 3%, 4%, or 5% chain loss plus 1.5% pulley loss.
Rougher surfaces raise the rolling-resistance coefficient.
Positive is a headwind; negative is a tailwind.
Positive climbs; negative descends. Enter rise over run as a percent.
Altitude above sea level; higher air is less dense.
Used only for mechanical work and calorie estimates.
Live results
Power at the pedals needed to balance modeled resistance at steady speed.
Pedal power divided by rider mass.
Power delivered after drivetrain loss.
Net modeled force opposing forward travel.
Estimated from elevation using a standard atmosphere.
Metabolic estimate using 24% gross efficiency.
Positive pedal power multiplied by ride duration.
Estimated pedal power 210.68 watts.
Power breakdown
| Component | Force | Wheel power | Pedal-equivalent power | Share of positive demand |
|---|
Where the pedal power goes
At the example settings, aerodynamic drag is the largest modeled demand.
How to use the Cycling Wattage Calculator
What this calculator does
This calculator estimates the steady pedal power required to maintain a selected ground speed. It adds the forces caused by road grade, tire-and-surface rolling resistance, and aerodynamic drag, multiplies the net force by speed, and then allows for chain and pulley losses. It also reports power relative to rider mass and estimates mechanical work and metabolic energy for a chosen ride duration. The model is useful for scenario planning, but it does not predict acceleration, cornering, braking, drafting, crosswinds, changing terrain, fatigue, or the exact reading of a particular power meter.
When to use it
Use it to compare riding positions at the same speed, estimate the extra demand of a climb or headwind, compare slick and knobby tires across surfaces, or check whether a target speed is plausible for a sustained training effort. It is also useful when planning equipment changes: the component table separates gravity, rolling resistance, aerodynamic drag, and drivetrain losses so you can see which assumption actually moves the result.
How to calculate
- The calculator opens with a complete demonstration: a 70 kg rider, an 8 kg bike, 35 km/h, aerobars, slick tires, a lubricated chain, asphalt, calm wind, level ground, sea-level elevation, and a 60-minute duration. The results and a validated example XLSX are available immediately.
- Choose Unit system. Switching between Metric and Imperial converts Your weight, Bike and gear weight, Speed, Wind speed, and Elevation while preserving the physical scenario.
- Replace the sample values and select Position, Tires, Chain, and Surface. Results update live. Read Estimated pedal power first, then use Power-to-weight ratio, the component table, and the bar chart to diagnose why the demand changed.
- Select Download Excel to export the current typed inputs, outputs, component detail, and model notes as a real Office Open XML workbook. Reset clears the demonstration data rather than restoring it; export is disabled until a complete valid state is entered again.
Input guide
Your weight is required and accepts a decimal mass from 20 to 250 kg, or the converted pound range in Imperial mode; 70 kg is the example. More rider mass increases climbing and rolling demand, but it does not directly increase aerodynamic drag in this model. Bike and gear weight is required from 2 to 80 kg; include bottles and luggage. A common mistake is entering rider-plus-bike mass in both fields, which double-counts weight.
Speed is required and must be greater than zero, up to 120 km/h or its mph equivalent. The example is 35 km/h. Higher speed increases all force-related power because power equals force times speed, while aerodynamic power rises especially quickly. Position is required and selects a CdA estimate: Tops 0.408, Hoods 0.324, Drops 0.307, or Aerobars 0.2914. It represents posture, not fitness. Tires and Surface are required and jointly determine the rolling coefficient; do not treat a rough-surface estimate as a laboratory tire ranking.
Chain is required and applies 3%, 4%, or 5% chain loss, plus a constant 1.5% pulley loss. Wind speed is required; positive values are headwinds and negative values are tailwinds. The apparent air speed cannot be negative, so a tailwind faster than your ground speed is rejected. Grade is required from – 30% to 30%; enter 5 for a 5% climb, not 0.05. Elevation is required from – 500 to 9,000 m and changes estimated air density. Ride duration is required from 1 to 1,440 minutes and affects only Mechanical work and Estimated calories, not instantaneous wattage. Numbers use a decimal point; ambiguous decimal-comma entries such as 1,5 are rejected rather than silently changed.
Output guide
Estimated pedal power is the modeled crank power in watts. A negative result means gravity assistance exceeds the resisting forces at the selected steady speed; it should be interpreted as coasting or braking demand, not negative human effort. Power-to-weight ratio divides pedal watts by Your weight in kilograms and is a comparison metric, not a training-zone prescription. Wheel power is net force times speed before drivetrain losses. Total resistance is the signed net force in newtons. Air density is the elevation-based atmospheric estimate. Estimated calories converts positive mechanical work using 24% gross efficiency, so it is an approximation rather than a nutrition prescription. Mechanical work is positive pedal power multiplied by duration.
The four header pills show Total mass, Apparent air speed, Total loss, and Rolling coefficient. The Power breakdown table lists each Component, its Force, Wheel power, Pedal-equivalent power, and Share of positive demand. The chart uses the same pedal-equivalent values for Gravity, Rolling resistance, Aerodynamic drag, and Drivetrain loss; bars share a zero baseline, so downhill assistance can extend left while resistive demands extend right.
Worked example
With the startup values, total mass is 78.00 kg and road speed is 9.722 m/s. Slick tires on asphalt use a rolling coefficient of 0.0050, producing about 3.825 N of rolling resistance. Aerobars use CdA 0.2914; at sea-level air density and no wind, aerodynamic drag is about 16.870 N. On level ground gravity contributes 0 N, so wheel power is approximately (3.825 + 16.870) × 9.722 = 201.20 W. A lubricated chain plus pulleys gives 4.50% total loss, so pedal power is 201.20 ÷ 0.955 = 210.68 W. Dividing by 70 kg gives 3.01 W/kg. For 60 minutes, the model reports about 758.46 kJ of mechanical work and 755.32 kcal of metabolic energy.
Learn more
The underlying force-and-power approach is consistent with the peer-reviewed validation study of a mathematical model for road cycling power. For unit interpretation, NIST explains the International System of Units, in which the watt is the derived unit of power. To interpret watts per kilogram in a training context, review British Cycling's explanation of cycling intensity measured with power.
How the cycling power model behaves
Pedal power = (gravity force + rolling force + aerodynamic force) × ground speed ÷ drivetrain efficiency.
Grade and mass dominate sustained climbing because the gravitational term is proportional to total mass and the sine of the road angle. On level ground, reducing weight has a smaller effect because only rolling resistance changes materially. Aerodynamic drag depends on air density, CdA, and the square of apparent air speed; after multiplication by ground speed, its power demand grows roughly with the cube of speed in still air. That is why a modest speed increase can require a large power increase on flat roads.
Wind is applied along the direction of travel. A headwind raises apparent air speed and drag; a tailwind lowers it. Real wind can include gusts and crosswind components, while a rider's effective CdA also changes with posture, clothing, equipment, yaw angle, and body dimensions. The position values here are scenario assumptions, not wind-tunnel measurements.
Rolling coefficients are representative combinations of tire tread and surface. Pressure, casing construction, temperature, load, texture, and vibration can change real rolling losses. Use the table to compare scenarios consistently rather than to claim laboratory precision. Likewise, the calorie estimate assumes steady positive power and average human efficiency. The CDC's general guidance on physical activity and health provides broader context, but this calculator does not provide medical or dietary advice.