FTP in Cycling: What It Is, How to Calculate It, and How to Use It in Your Training
If you have a power meter and don't know your FTP, you're pedaling blind. FTP (Functional Threshold Power) is the number that turns all those watts into useful information: it determines your training zones, measures your progress, and lets you compare sessions with objective precision.
In this article I'll explain what FTP is, how to calculate it correctly, how to use it to structure your training, and how often you should update it.
What Is FTP
FTP is the maximum average power you can sustain for 60 minutes. In practice, it represents your anaerobic threshold: the intensity at which lactate starts accumulating faster than your body can clear it.
Above FTP, lactate accumulation is exponential and the effort becomes unsustainable within minutes. Below FTP, you can sustain the effort for hours with proper training.
FTP is measured in watts (W) and also expressed as watts per kilogram (W/kg) to compare between cyclists of different weights. An average amateur cyclist typically has an FTP between 2.5 and 3.5 W/kg. Elite professional cyclists exceed 6 W/kg.
How to Calculate Your FTP: The 20-Minute Test
The most widely used test to calculate FTP doesn't last 60 minutes but 20. The average power of those 20 minutes, multiplied by 0.95, gives a good estimate of the real FTP.
20-minute test protocol:
- 20–30 minute warm-up at low-moderate intensity, with 2–3 short 30-second accelerations to activate the neuromuscular system.
- 5 minutes at maximum intensity to deplete creatine phosphate stores and stabilize metabolism (this makes the 20-min test more representative of real FTP).
- 5 minutes of easy recovery.
- 20 minutes at maximum sustainable effort. The key is starting at an intensity you can hold to the end — not going all out and collapsing at minute 10. Power should be relatively constant or slightly increasing.
- 10–15 minute cool-down.
Your estimated FTP = average power over 20 minutes × 0.95
Example: if your average power over 20 minutes was 280W, your estimated FTP is 280 × 0.95 = 266W.
Alternatives to the 20-Minute Test
The 20-minute test is demanding and requires good conditions (prior rest, motivation, controlled environment). Alternatives exist:
| Method | Duration | Accuracy | Best for |
|---|---|---|---|
| 20 min test × 0.95 | ~60 min total | High | Cyclists experienced with testing |
| 8 min test × 0.90 | ~45 min total | Medium-high | Beginners or highly fatigued riders |
| Ramp test | ~20–30 min | Medium | Frequent testing, lower fatigue |
| Calculation from peak powers (MPA) | No dedicated test | Variable | Platforms like TrainingPeaks or WKO |
How to Use FTP to Structure Your Training Zones
Once you have your FTP, you can calculate power-based training zones. The most widely used model is Andrew Coggan's 7-zone system:
- Z1 Active recovery: <55% FTP
- Z2 Endurance: 55–75% FTP
- Z3 Tempo: 76–90% FTP
- Z4 Threshold: 91–105% FTP
- Z5 VO2max: 106–120% FTP
- Z6 Anaerobic capacity: 121–150% FTP
- Z7 Neuromuscular power: >150% FTP
With an FTP of 266W, your zone 2 (aerobic base) falls between 146W and 199W. Those are the watts at which your long rides and base sessions should be done.
How Often Should You Update Your FTP
FTP changes with training. If you've completed a consistent 6–8 week training block, it's likely gone up. If you've been sick, rested, or reduced volume, it may have dropped slightly.
Practical rules:
- Test every 6–8 weeks during active training season.
- Don't test during a high-load week or after an important race.
- If during a training session you clearly exceed your zone 4 watts without feeling near your limit, that's a sign your real FTP is higher than estimated.
FTP and Your Strava Data
Strava lets you set your FTP in your profile and automatically calculates Training Load and Estimated Best Efforts for each activity. If your FTP in Strava is outdated, all those metrics will be incorrect.
Beyond Strava, what truly matters is using FTP to design each session with purpose. Every work block at Z3, Z4, or Z5 should be justified by the goal of that session and your accumulated fatigue level.
Iron Buddy analyzes your Strava activities and, if your FTP is set, evaluates whether your training intensity distribution is consistent with your goal and season phase. If you're doing too much tempo (Z3) and too little base or real quality work, it will tell you.
Connect your Strava to Iron Buddy and get an analysis of your power and intensity distribution.