Cycling FTP Calculator
Cycling FTP, W/kg, and Zone 2 from 20-minute power.
What it does
Functional threshold power condenses fitness into one wattage: the most a rider holds for about an hour. Allen and Coggan estimate it at 95 % of best 20-minute power, so a 250 W test means roughly 237.5 W threshold. Zones, pacing, and progress all hang off that number.
The tool above runs the method in both unit systems. Enter 20-minute power and weight, and it prints FTP, watts per kilo, and the Zone 2 endurance band. Defaults give 237.5 W at 3.17 W/kg with Zone 2 at 133 to 178 W.
Authorities confirm each constant. British Cycling defines FTP as 60-minute power with the 30-minute test protocol and shows 250 W becoming 238 W, while TrainingPeaks prints Coggan zones from the Allen and Coggan book. University repository work validates the 95 % estimate against hour power.
Protocol decides comparability. Rested legs, calibrated meters, and similar courses keep tests honest; heat and fatigue bend single results. Retest on the same setup and chase the trend across months, not one heroic number.
How to use
- Pick metric (kg) or imperial (lb).
- Enter best 20-min mean power.
- Enter rider weight.
- Read FTP first, then W/kg.
- Read Zone 2 for endurance rides.
- Retest on the same protocol.
Formula
- power
- Best 20-min mean watts, to 3,000.
- weight
- Rider mass: kg or lb by system.
- 0.95
- 95 % factor for the 60-min estimate.
British Cycling confirms 0.95 with a 250-to-238 worked example; TrainingPeaks prints Coggan zones (Z2 55-74 shown as 56-75 here).
Worked example
Example: 250 W, 75 kg
Metric defaults: 250 W, 75 kg. Imperial mirrors at 165.3 lb.
- Inputs: 250 W best 20 minutes, 75 kg rider.
- FTP: 250 x 0.95 = 237.5 W.
- W/kg: 237.5 / 75 = 3.17.
- Zone 2: 0.56 x 237.5 = 133 to 0.75 x 237.5 = 178 W.
- Tool shows 237.5 W, 3.17 W/kg, 133 to 178 W.
Reference table
| 20-min / FTP | W/kg at 75 kg | Zone 2 |
|---|---|---|
| 200 / 190.0 W | 2.53 | 106 to 143 W |
| 250 / 237.5 W | 3.17 | 133 to 178 W |
| 300 / 285.0 W | 3.80 | 160 to 214 W |
| 350 / 332.5 W | 4.43 | 186 to 249 W |
Limits
- Estimate only. Hour tests rule for precision.
- Ignores heat, altitude, and fatigue shifts.
- Meter calibration errors carry straight in.
- Zones simplify individual physiology.
Common mistakes
- Testing tired and calling it threshold.
- Uncalibrated meters inflating watts.
- Mixing protocols across retests.
- Training zones from stale FTP.
- Chasing single-test heroics.
Try it yourself
Quick checks. Answers sit tucked under each question.
300 W, 80 kg?
FTP 0.95 x 300 = 285 W. W/kg 285 / 80 = 3.56. Z2 160 to 214 W.
200 W, 65 kg?
FTP 0.95 x 200 = 190 W. W/kg 190 / 65 = 2.92. Z2 106 to 143 W.
Questions
How is FTP figured?
95 % of best 20-minute mean power, per Allen and Coggan. Here 0.95 x 250 = 237.5 W.
What is W/kg?
FTP over kilograms. Here 237.5 / 75 = 3.17 W/kg for comparing riders.
What is Zone 2 range?
56 to 75 % of FTP for endurance: 133 to 178 W here. Zone bounds follow Coggan tables.
How do I test 20 minutes?
Ride 30 minutes hard, average the final 20, subtract 5 %. British Cycling uses this protocol.
Does protocol matter for retests?
Yes. Same course, rested legs, calibrated meter, similar conditions. Trends beat single tests.
What shifts results?
Yes. Heat, altitude, fatigue, and meter drift all move results; note conditions per test.
Sources
- British Cycling: Understanding Power (FTP 0.95 method)
- TrainingPeaks: Coggan Power Zones (book zones)