FTP Calculator

Functional Threshold Power. Roughly the average power you could hold for an hour. It's the anchor most cycling training plans use to define zones.

The horizontal asymptote of your power-duration curve, in watts. It's the power you could in theory hold indefinitely on aerobic energy alone. CP is closely related to FTP but typically sits about 3% higher (Karsten et al. 2020 measured CP at 256 W against FTP at 249 W in trained cyclists). To get CP from this calculator, switch to the Multiple efforts tab and enter two or more maximal efforts at different durations.

Anaerobic work capacity, in kilojoules. The budget of work you can spend above CP before you have to back off. Typical values: 12 to 18 kJ for endurance riders, 20 to 25 kJ for all-rounders, 25 to 35 kJ for sprinters. With two or more maximal efforts the calculator fits W' directly from your data. With one effort it assumes 22 kJ as a population average.

Closely related, not identical. CP is the curve's asymptote, computed from the math. FTP is your 60-minute sustainable power, used to define training zones. CP usually comes out a few watts higher (around 3%). This calculator reports FTP = 0.97 × CP, which is the middle of the published range. Coggan-style zones are defined off FTP, not CP, so use FTP for your zone targets.

For a 5 to 30 minute single effort the output matches intervals.icu within a watt or two, because both use the same Morton 3-parameter model. The main source of error in single-effort mode is your anaerobic capacity (W'). The calculator assumes 22 kJ as a population average; sprinter types carry more, long-distance diesels carry less. To remove that assumption switch to the Multiple efforts tab and enter two or more tests, and the calculator fits W' directly from your data.

For a single effort the 20-minute test is what most coaches recommend. A long warm-up, then 20 minutes flat out. The calculator takes 95% of your average and treats that as FTP. The number is consistent across days as long as you can pace it well. For a multi-effort critical-power fit, do two or three maximal efforts at well-spaced durations (for example 3 min and 12 min, or 5 min and 20 min). Bunching efforts within 2x of each other leaves CP and W' poorly constrained.

It's consistent if you can pace it. Go out too hard and the number is junk. Ramp tests are easier to execute, but they map FTP from your final 1-minute power, which is the noisiest part of the power-duration curve. The 8-minute test sits in between. If your W' is well off the population average (rouleurs low, sprinters high), a multi-effort CP fit will read closer to truth than any single-duration test.

Every 6-8 weeks during a structured training block. More often isn't useful because FTP doesn't shift that fast, and a max test costs you a training day. Wait until you're rested. A low-form test gives a low number, and that throws your zones off for the whole next block.

Coggan's tables split into men's and women's bands. For men: untrained below 2.5, fair 2.5-3.0, moderate 3.0-3.5, good 3.5-4.0, very good 4.0-4.5, excellent 4.5-5.0, exceptional 5.0-5.5, world class above 5.5. Women's bands sit roughly 0.5 W/kg lower at each step. The calculator uses whichever table you pick. The labels matter less than whether your number is trending up.

Not really. The model assumes the effort is mostly aerobic, which only starts being true around the 3-minute mark. Below that, anaerobic capacity is doing most of the work, and that varies hugely between riders. You can have a huge 1-minute number and an ordinary FTP.

Body weight only. W/kg is a physiology metric, so the bike doesn't factor in. For speed or climbing rate, which do depend on bike weight, use the bike-split calculator.

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