Functional threshold power from a 20-minute test, and your zones in watts
Updated October 2026
Choose the 20-minute option if you have the average power from an all-out 20-minute test; the calculator takes 95% of it. Choose "My FTP already" if your training app or a lab test gave you an FTP, and it is used as is. Power must come from a power meter or a smart trainer that measures power; estimated "virtual power" on basic trainers can be far off. Weight is optional and only feeds the watts-per-kilogram line. The results show FTP, W/kg and the watt range of each of the seven zones.
Warm up well, then ride as hard as you can sustain for exactly 20 minutes on a flat road or a smart trainer, pacing evenly. Multiply the average power by 0.95 to estimate the power you could hold for about an hour. In a study of 46 road cyclists, FTP measured this way was higher than power at the ventilatory threshold and correlated very strongly with power at the respiratory compensation point; a 2022 study by the same group found correlations of r = 0.68 to 0.93 with lactate thresholds. The authors caution that it is an estimate, not a substitute for lab testing.
263 W × 0.95 = 249.85, rounded to an FTP of 250 W. Each zone boundary is FTP times its percentage, rounded: endurance runs from 0.56 × 250 = 140 W to 0.75 × 250 = 187.5, shown as 188 W. Here are the zones for three FTPs:
| Zone | % of FTP | FTP 200 W | FTP 250 W | FTP 300 W |
|---|---|---|---|---|
| Z1 Active recovery | ≤55% | up to 110 W | up to 138 W | up to 165 W |
| Z2 Endurance | 56–75% | 112–150 W | 140–188 W | 168–225 W |
| Z3 Tempo | 76–90% | 152–180 W | 190–225 W | 228–270 W |
| Z4 Threshold | 91–105% | 182–210 W | 228–263 W | 273–315 W |
| Z5 VO2 max | 106–120% | 212–240 W | 265–300 W | 318–360 W |
| Z6 Anaerobic | 121–150% | 242–300 W | 303–375 W | 363–450 W |
| Z7 Neuromuscular | >150% | over 300 W | over 375 W | over 450 W |
The seven zones follow Allen and Coggan’s power-training levels (Training and Racing with a Power Meter, 3rd edition, 2019). Zone 1 (up to 55%) is recovery spinning. Zone 2 (56-75%) builds endurance and makes up most training time for many riders. Zone 3 (76-90%) is tempo; Zone 4 (91-105%) is threshold work such as 2 × 20 minutes. Zone 5 (106-120%) targets VO2 max with intervals of a few minutes, Zone 6 (121-150%) short anaerobic efforts, and Zone 7 all-out sprints, which are better judged by effort than by a watt target. Retest every 6 to 8 weeks or after a training block, because zones move with fitness.
| Rider weight | FTP 250 W | FTP 300 W |
|---|---|---|
| 130 lb (59.0 kg) | 4.24 W/kg | 5.09 W/kg |
| 150 lb (68.0 kg) | 3.67 W/kg | 4.41 W/kg |
| 165 lb (74.8 kg) | 3.34 W/kg | 4.01 W/kg |
| 185 lb (83.9 kg) | 2.98 W/kg | 3.58 W/kg |
| 210 lb (95.3 kg) | 2.62 W/kg | 3.15 W/kg |
Power-to-weight decides climbing speed, because on steep grades most of your power goes into lifting rider and bike. On flat roads, aerodynamic drag dominates, so absolute watts and position matter more than weight. Use body weight on the test day.
Starting too hard and fading lowers the average; aim for even power. Testing tired after hard days understates FTP. Comparing indoor and outdoor tests: heat and a fixed position lower power indoors for many riders, so set indoor zones from an indoor test. Switching power meters between tests can shift the numbers. Applying 95% to a ramp test is wrong; ramp tests use their own factor set by the app. Retesting too rarely leaves zones that no longer match your fitness.
FTP estimates one point on your fitness curve. It does not measure sprint power, endurance over several hours or how quickly you recover, and a field test is not a medical test. A 20-minute all-out effort is vigorous exercise: the American College of Sports Medicine’s screening guidance is to get medical clearance first if you have known heart, kidney or metabolic disease or symptoms of it and are not already exercising regularly. Stop the test and seek care for chest pain or pressure, fainting or near-fainting, unusual breathlessness, or a racing or irregular heartbeat.