Formula used
How to use this calculator
- Select the test method that matches your last indoor or outdoor test.
- Enter the required power value(s) in watts. Add body weight to see W/kg.
- Press Calculate to view FTP, zones, and pacing tips above.
- Use CSV for spreadsheets and PDF for sharing.
- Retest every 4–8 weeks and compare the exported reports.
Example data table
Sample estimates using typical test inputs. Your results depend on protocol, pacing, fatigue, and equipment.
| Rider | Method | Input | Estimated FTP (W) | Weight (kg) | W/kg |
|---|---|---|---|---|---|
| A | 20‑min | 20‑min avg = 240 W | 228.0 | 70 | 3.26 |
| B | 8‑min | 280 W, 270 W | 247.5 | 78 | 3.17 |
| C | Ramp | 1‑min finish = 340 W | 255.0 | 64 | 3.98 |
| D | Known | FTP entered = 300 W | 300.0 | 75 | 4.00 |
Training relevance of FTP
Functional Threshold Power estimates the highest steady power you can sustain near one hour. It anchors training targets because it adapts to fitness, fatigue, and equipment. When FTP rises, the same workout feels easier at the same watts. When FTP drops, zones prevent you from overreaching. Riders commonly plan weekly load by combining endurance volume with controlled threshold work.
Test selection and pacing data
The 20-minute option uses 0.95 × P20 to reduce anaerobic influence. Two 8-minute efforts use 0.90 × average(P8A, P8B) and often suits riders with strong repeatability. Ramp conversion uses 0.75 × best 1-minute finish power and is sensitive to cooling, trainer resistance, and cadence. For best data, include a 15–20 minute warm-up, then pace the effort evenly, avoiding early spikes.
Interpreting watts per kilogram
W/kg helps compare performance across body sizes. For example, 250 W at 75 kg equals 3.33 W/kg, while 250 W at 62 kg equals 4.03 W/kg. Use W/kg for climbing goals, but still track absolute watts for flat time-trial speed and group riding dynamics.
Zone ranges and workout construction
Zones in this calculator follow Coggan-style percentages of FTP: recovery below 55%, endurance 56–75%, tempo 76–90%, threshold 91–105%, VO₂ 106–120%, anaerobic 121–150%, and neuromuscular above 150%. Build sessions by time-in-zone, such as 3×12 minutes at 95–100% with equal recovery. For endurance, try 90 minutes at 65–75% to build aerobic capacity with manageable fatigue.
Tracking progress with exports
Exported CSV is ideal for spreadsheets and long-term charts. PDF is helpful for sharing with a coach, team, or training partner. Re-test every 4–8 weeks under similar conditions, then compare FTP, W/kg, and how your zone boundaries shift. Log test date, protocol, and average cadence; if FTP changes by less than 2–3%, consider it normal noise and focus on consistent workouts instead over several weeks before retesting.
Data quality and practical limits
Power meters differ by 1–3%, and indoor trainers can vary more if tire pressure or calibration changes. Keep the same device, firmware, and setup when possible. Treat this estimate as a planning baseline, then adjust zones if workouts feel consistently too easy or too hard. Record temperature, nutrition, and sleep, because they affect repeatability across tests and explain short-term variability.
FAQs
1) Is FTP the same as one-hour best power?
Not always. FTP is a practical estimate of sustainable threshold power. Many riders sit slightly above or below their true 60-minute best depending on fatigue resistance and pacing.
2) Which method should I use?
Use the method you can repeat reliably. The 20-minute test is common outdoors, the 8-minute option fits repeatable efforts, and ramp tests work well indoors with strong cooling.
3) Why does my ramp-based FTP feel too high?
Riders with strong anaerobic contribution can score high on ramps. If threshold intervals feel unsustainable, reduce FTP by 2–5% and reassess after two weeks of consistent training.
4) How often should I retest?
Every 4–8 weeks is typical. Retest sooner after a structured block or major fitness change, and later during maintenance phases where training intensity and volume stay stable.
5) What is a good W/kg value?
It depends on discipline and terrain. Higher W/kg helps on climbs, while absolute watts matter on flats. Track your own trend over time and compare results from similar conditions.
6) Do zones change if I use heart rate instead of power?
Heart rate responds slower and is influenced by heat, hydration, and stress. Power zones are immediate and precise. If you use heart rate, expect broader ranges and day-to-day variability.