About the FTP Calculator
Functional threshold power (FTP) is the highest average power a cyclist can sustain for roughly an hour, and it anchors almost every power-based training plan. Riding a true 60-minute time trial is hard to do well, so most riders estimate FTP from a shorter test. This FTP calculator converts the result of the most popular protocols into an FTP estimate and shows it in watts and watts per kilogram.
Choose the test you rode: the classic 20-minute test (95% of average power), the 2 × 8-minute test (90% of the average of both efforts), a ramp test (75% of your best one-minute power), a full 60-minute effort, or the two-effort critical power model using an all-out 3-minute and 12-minute effort. The critical power option also reports W′ (W-prime), the work you can do above threshold before fatiguing.
Use it after an indoor trainer test, a club time trial or a hill effort to update your zones. The conversion factors are averages — riders with big anaerobic engines tend to be overestimated by short tests — so sanity-check the number with a 30–40 minute steady effort at your new FTP.
With the default inputs, the estimated ftp is 238 W. Change any value above to recalculate instantly.
How to use the ftp calculator
- 1Warm up well and ride your chosen test all-out but evenly paced.
- 2Select the test type you completed.
- 3Enter the average power (or best 1-minute power for a ramp test).
- 4Add your body weight to see watts per kilogram.
- 5Copy the zone table into your head unit or training app.
Formula and method
Short tests overestimate the power you can hold for an hour, so each is scaled down: 95% of a 20-minute average (Allen and Coggan’s classic protocol), 90% of the average of two 8-minute efforts, and 75% of the best one-minute power at the end of a ramp test (the factor used by most indoor training apps). A well-paced 60-minute effort is FTP by definition.
The critical power model treats total work as CP × time + W′. With two all-out efforts at 3 minutes (180 s) and 12 minutes (720 s), CP is the slope of work versus time, (P12 × 720 − P3 × 180) ÷ (720 − 180), and W′ is the extra work done above CP in the short effort. CP is typically close to FTP. Zones use the Coggan percentages.
- P20, P8, P60
- Average power for the 20-, 8- or 60-minute effort (W)
- P1(ramp)
- Best one-minute power in a ramp test (W)
- CP
- Critical power (W)
- W′
- Work capacity above critical power (J or kJ)
Worked examples
20-minute test at 250 W, 75 kg rider
FTP = 250 × 0.95 = 237.5 W. Divided by 75 kg that is 3.17 W/kg. Sweet-spot work would sit at roughly 209–223 W.
Ramp test, best minute 320 W, 154 lb
A ramp test FTP is 75% of the best one-minute power: 320 × 0.75 = 240 W. 154 lb is 69.85 kg, so the rider produces about 3.44 W/kg.
Critical power from 3-min 350 W and 12-min 280 W
CP = (280 × 720 − 350 × 180) ÷ 540 = (201,600 − 63,000) ÷ 540 = 256.7 W. W′ = (350 − 256.7) × 180 = 16,800 J, or 16.8 kJ of work available above CP.
Frequently asked questions
What is FTP in cycling?+
Functional threshold power is the highest average power you can sustain in a quasi-steady state for about an hour. Training zones, TSS and intensity factor are all calculated as percentages of it, so an accurate FTP makes every workout more precise.
Why multiply a 20-minute test by 0.95?+
You can hold slightly more power for 20 minutes than for 60 because part of the effort is fuelled anaerobically. Taking 95% of the 20-minute average removes that extra and approximates hour power for most trained riders.
Is a ramp test accurate for FTP?+
It is convenient and repeatable, but it measures how long you last as power climbs every minute. Riders with strong anaerobic capacity can score high and find intervals at the resulting FTP too hard; diesel-type riders may be underestimated.
What is a good FTP in watts per kg?+
Watts per kilogram matters more than raw watts on climbs. Many untrained adults start around 2 W/kg, regular club riders often reach 3–4 W/kg, and professional road racers sit well above 5 W/kg.
How often should I test FTP?+
Every 4–8 weeks during a training block is typical, or whenever workouts start to feel consistently too easy or too hard. Test under the same conditions — same trainer, warm-up, time of day and fuelling.