health · 2026-05-01
Estimate functional threshold power (FTP) from a 20-minute test using the standard 95% multiplier, plus power-zone targets.
| 20-minute test average watts | 245 |
| Rider weight (lb) | 165 |
| Power-to-weight (W/kg) | 3.11 |
| Z1 active recovery upper (W) | 128 |
| Z2 endurance upper (W) | 175 |
| Z3 tempo upper (W) | 209 |
| Z4 threshold (95-105% FTP) lower (W) | 212 |
| Z5 VO2max (106-120% FTP) lower (W) | 247 |
FTP is the highest average power you can sustain for ~1 hour. It's the single most important number in cycling training because every interval prescription, every zone, every TSS calculation is anchored to it.
A true 60-minute all-out test is brutally hard, mentally and physically. Most riders can't pace it accurately. The 20-minute test is shorter, easier to pace, and the 0.95 multiplier accounts for the fact that you can hold ~5% more power for 20 minutes than for 60.
Alternatives: 8-minute test × 0.90, or ramp test (less accurate but indoor-trainer friendly).
Pure power matters on flat. Power-to-weight matters on hills. The Coggan power profile chart classifies riders:
Pro Tour climbers ride ~6.0-6.5 W/kg sustained on a 30-minute climb.
The same Z1-Z5 framework as HR, plus Z6 (anaerobic) and Z7 (neuromuscular sprints). Power has the advantage over HR of being immediate — when you push the pedals harder, watts respond instantly, while HR has 30-90 second lag.
Every 6-8 weeks during structured training. Significant FTP changes happen across training blocks, not within them. More often than that and you're testing instead of training.
Indoor FTP is usually 5-15 watts lower than outdoor due to heat buildup and lack of cooling airflow. Use indoor-derived FTP for indoor sessions and outdoor-derived FTP outdoors. A direct-drive trainer with a fan helps close the gap.
For structured training, yes. HR-based intervals are 30+ seconds late on every transition and don't reflect short hard efforts well. Power tells you exactly what you're doing in real time. Smart trainers (Wahoo Kickr, Tacx Neo) include a power meter; pedal-based meters (Garmin Vector) work outside.
Power-to-weight matters more than absolute. A 250W FTP at 145 lb (3.8 W/kg) is more impressive than 280W at 195 lb (3.15 W/kg) on any climb. Compare yourself against the Coggan chart at your weight, not against your friend's absolute number.