Find out how many watts a ride takes, or how fast your watts will take you. Gradient, wind, aerodynamics, tires and drivetrain are all in the model.
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Estimated cycling power based on the inputs provided. Real-world power can differ because of equipment, road surface, wind variability and rider position.
If you only want a ballpark, these two tables answer the question without entering anything. Both assume an 8 kg road bike, hands on the hoods, standard wheels, race tires, a clean drivetrain, sea level and no wind, and every figure is calculated by the same model as the tool above. They show watts at the pedals.
| Speed | 60 kg rider | 75 kg rider | 90 kg rider |
|---|---|---|---|
| 20 km/h (12.4 mph) | 48 W | 51 W | 54 W |
| 25 km/h (15.5 mph) | 85 W | 89 W | 92 W |
| 30 km/h (18.6 mph) | 139 W | 143 W | 147 W |
| 35 km/h (21.7 mph) | 213 W | 217 W | 222 W |
| 40 km/h (24.9 mph) | 310 W | 315 W | 321 W |
| 45 km/h (28 mph) | 434 W | 440 W | 446 W |
| Speed | 60 kg rider | 75 kg rider | 90 kg rider |
|---|---|---|---|
| 8 km/h (5 mph) | 100 W | 122 W | 143 W |
| 10 km/h (6.2 mph) | 127 W | 154 W | 181 W |
| 12 km/h (7.5 mph) | 154 W | 187 W | 219 W |
| 15 km/h (9.3 mph) | 199 W | 239 W | 279 W |
| 18 km/h (11.2 mph) | 246 W | 295 W | 343 W |
Read across the flat table and weight barely matters; read across the climbing table and it decides everything. That split explains most of cycling power, and the next section shows where it comes from.
At a steady speed, the power you put through the pedals equals the sum of the forces resisting you, multiplied by speed, divided by how efficiently the drivetrain passes power to the wheel:
Here g is 9.80665 m/s² and grade is the gradient as a fraction. It is zero on flat ground, positive uphill and negative downhill, where gravity pays you back. This is why weight dominates the climbing table above.
CdA is your drag coefficient multiplied by your frontal area. Air density falls with altitude, so the same speed costs fewer watts up high. Drag force rises with the square of airspeed, and since power is force times speed, drag power rises with the cube.
Crr is the tire and surface coefficient. It multiplies weight, not speed, so this force is constant and the power it costs grows only linearly with speed.
A chain and two derailleur pulleys convert a few percent of your effort into heat. The calculator multiplies the chain and pulley efficiencies together and divides the wheel power by that figure.
| Input | Values used | Source |
|---|---|---|
| Riding position (CdA, m²) | tops 0.408, hoods 0.324, drops 0.307, aerobars 0.2914 | Jeukendrup, High-Performance Cycling (2002) |
| Wheelset (CdA reduction) | standard 0%, aero 3%, super-aero 5% | Cyclist magazine aero-wheel figures (an estimate) |
| Tire rolling resistance (Crr) | road race 0.00321, road winter 0.00606, gravel fast 0.00722, gravel aggressive 0.00809 | BicycleRollingResistance.com lab tests (paved surface) |
| Chain loss | new 3%, dry 4% | Ridefar drivetrain-efficiency testing |
| Derailleur pulley loss | steel bushing 2%, steel bearing 1.5%, ceramic bearing 1%, oversized ceramic bearing 0.5% | Ridefar drivetrain-efficiency testing |
Air density uses a scale-height approximation, 1.225 kg/m³ at sea level falling exponentially with elevation. Advanced mode lets you override CdA and Crr with your own measured values.
A 75 kg rider on an 8 kg bike, hands on the hoods, standard wheels and race tires, at sea level:
That is 2.27 W/kg, and about 86% of the power that reaches the wheel is spent on air.
The same rider now spends most of the effort lifting mass. Air drag has shrunk to a minor term.
Hold 32 km/h into a 5 m/s (18 km/h) headwind and you need 380 W. With the same wind behind you, it is 52 W. The headwind adds 210 W while the tailwind saves only 118 W, because drag depends on the square of airspeed.
A steady 250 W holds about 36.8 km/h on the flat and only about 15.6 km/h up a 6% climb. Enter the same numbers above in Watts to Speed mode to confirm.
Changing one thing at a time and holding everything else fixed gives a clear ranking. Positive numbers are watts saved by the change; the headwind row is negative because it costs watts.
| Change | Where | Watts |
|---|---|---|
| Hands from the hoods to the drops | 32 km/h, flat | 7.7 W |
| Hands from the hoods to aerobars | 32 km/h, flat | 14.7 W |
| Hands from the tops to the hoods | 32 km/h, flat | 37.8 W |
| Standard wheels to deep-section aero wheels | 32 km/h, flat | 7.3 W |
| Winter training tires to race tires | 32 km/h, flat | 21.6 W |
| Dry, worn chain to a clean lubricated chain | 32 km/h, flat | 1.8 W |
| A 5 m/s (18 km/h) headwind instead of still air | 32 km/h, flat | -210.3 W |
| 5 kg less rider weight | 12 km/h, 7% climb | 12.5 W |
| 1 kg less bike weight | 12 km/h, 7% climb | 2.5 W |
| Winter training tires to race tires | 12 km/h, 7% climb | 8.1 W |
On the flat, wind and riding position lead, tires come next and the chain barely registers. On a climb, body mass dominates and a lighter bike is worth little compared with a lighter rider. Your drag area is a big lever you control. The CdA calculator measures it, the aero watts calculator prices it in watts, and the rolling resistance calculator does the same for tires.
The calculator reports watts per kilogram beside the total, because two riders producing the same watts are very different athletes at 60 kg and 90 kg. For context, the Allen and Coggan power profile groups FTP-level W/kg like this, with separate columns for men and women. Each value is the chart's printed figure for that rating, and your own result belongs to the nearest one. It is a rough guide for young adult racers, not a verdict:
| Rating | Men, FTP in W/kg | Women, FTP in W/kg |
|---|---|---|
| Untrained | 2.22 | 1.83 |
| Fair | 2.75 | 2.32 |
| Moderate | 3.29 | 2.82 |
| Good | 3.82 | 3.31 |
| Very Good | 4.44 | 3.88 |
| Excellent | 4.98 | 4.38 |
| Exceptional | 5.51 | 4.87 |
| World Class | 6.04 | 5.36 |
The watts a ride needs are not the same as the watts you can sustain. To see where a ride sits against your fitness, compare the result with your threshold from the FTP calculator, and use the W/kg calculator for your own power-to-weight ratio.
Once you know the watts, the next question is usually time. If you want a quick pace and finish time from a power number, the cycling speed calculator is the shorter route. For a specific hill, the hill climb calculator turns your power and weight into a climbing time, and the VAM calculator goes back the other way, from a finished climb to a vertical ascent rate you can compare across mountains.
Weight, gradient and speed are easy to get right. The two inputs most riders guess are aerodynamic drag and tire rolling resistance. If you have a steady ride with a power meter, the CdA calculator works your drag area out from it, and you can type that number into advanced mode in place of the position presets. The tire table in the rolling-resistance tool does the same job for Crr. Replace the two guessed inputs with measured ones and the calculator's answer tightens noticeably.
A ride's watts only mean something next to your own limits. Start by finding your threshold with the FTP calculator, then turn it into the seven Coggan training zones in the power zones calculator. The critical power calculator adds W′, the finite reserve above threshold that governs surges and sprints. After each ride, the TSS calculator scores the training stress it added.
The model is the standard classical-mechanics one used by most bike-power tools, and given accurate inputs it typically lands within a few percent of a power meter on steady, solo, constant-speed rides on a smooth road. It assumes constant speed, a single wind value with no yaw-angle modeling, no drafting, and riding position fixed for the whole ride. Acceleration, braking, cornering, stop-start traffic and pack riding all break those assumptions.
Use it to plan, compare and understand: what a headwind costs, what an aero upgrade is worth, which gear and pace make a target time realistic. Use a power meter to record what actually happened. The full method is on the methodology page, every citation is on the sources page, and the about page explains who the site is for.
Estimate your FTP, set training zones, see what your tires cost in watts or predict a climb time. Every calculator is free, runs in your browser and shows the formula and sources behind its answer.
Cycling power, FTP, watts per kilogram and performance modeling.
Speed, hill climbing, and vertical ascent performance.
Training stress, workload and intensity.
The forces behind cycling power: drag, rolling resistance and drivetrain loss.
