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Functional Threshold Power Calculator

Estimate cycling FTP from a 20-minute power test

How it is calculated

The tool applies one multiplier: FTP = 0.95 × P20. P20 is your average power in watts over a maximal, evenly paced 20-minute effort, as read from a power meter or smart trainer. The result is rounded to a whole watt. Power must be above zero, otherwise nothing is returned. The 95% factor is a standard shortcut that assumes the 20-minute effort overstates what you could hold for an hour; it does not adjust for rider type, so strong sprinters and endurance specialists can differ. The tool gives FTP only; it does not compute training zones or W/kg, which you get by dividing FTP by body weight in kilograms.

Worked example

After a warm-up you ride a 20-minute all-out test and your power meter shows an average of 265 W. FTP = 0.95 × 265 = 251.75, which the tool rounds to 252 W. If you weigh 70 kg, that is about 3.6 W/kg, a figure you can compare between tests as fitness changes.

Try this example →

Common mistakes

  • Using the average of the whole ride instead of the 20-minute test segment. Warm-up and recovery watts pull the number far below your real FTP.
  • Starting the test too hard and fading. An even effort gives a true average; a blown start leaves you with an underestimated 20-minute number.
  • Entering normalized power or the best peak 5-minute power. The field expects the plain average power over 20 minutes.
  • Applying the 95% twice, for instance by typing a value you already multiplied by 0.95. The tool does that step itself.
  • Testing on a different bike or trainer from the one you train on, so the numbers do not match your usual power meter.

Sources

About this calculator

Functional Threshold Power is estimated as 95% of your average power output over an all-out 20-minute effort — a proxy for the power you could theoretically sustain for a full hour, without needing to actually suffer through a 60-minute test.

Coined by Andrew Coggan and now standard in cycling training software like TrainingPeaks and Zwift, FTP anchors every training zone a cyclist uses — zone 2 endurance rides, threshold intervals, VO2max efforts — all defined as percentages of it, and it's re-tested every few weeks so training zones stay accurate as fitness improves.

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Comments (1)

  • Editorial team

    Once you have an FTP, the number only becomes useful when you attach it to your training plan. This tool returns FTP alone, so apply your plan's zone percentages yourself: a plan that puts endurance at 56 to 75 percent of FTP would mean roughly 141 to 189 W for the 252 W result in the guide. Retest under the same conditions, bike and trainer. Which test do you prefer, 20-minute or a ramp test?

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