Power capacity tool

FTP Calculator

Estimate cycling FTP from a ride file (GPX, FIT, or TCX) or a 20-minute field test. Critical Power and W' can appear as secondary outputs.

What does an FTP calculator estimate?

An FTP calculator estimates Functional Threshold Power, the cycling threshold used for power zones and workout targets. This tool can estimate FTP from a GPX, FIT, or TCX ride file, or from a 20-minute field test. Critical Power and W' may appear as secondary outputs; the Critical Power calculator owns CP fitting from MMP points.

Test protocol
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Weight (kg) Optional
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Supports GPX / TCX / FIT (single file)

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How to use the FTP calculator

1

Choose your test protocol

Select the protocol that matches the uploaded activity, such as a 20-minute FTP test (30-minute TT), 3/9-minute, or 10K.

2

Upload one activity file

Use a GPX, FIT, or TCX file from the test effort. Add body weight if you want W/kg context.

3

Review FTP first

Treat the FTP estimate as the primary result. Use any CP and W' values as secondary context, then compare with repeat tests and training feedback.

Test protocol guide

For more comparable and reliable estimates, follow a standard protocol as consistently as possible. This tool is tuned for these protocols.

3/9-minute all-out test
  1. Warm-up: 10 minutes easy, then 5 × 100 m strides (~80% effort).
  2. Test 1: 3 minutes all-out (hold the best sustainable pace/power).
  3. Recovery: 30 minutes easy (walk/jog mix).
  4. Test 2: 9 minutes all-out (hold the best sustainable pace/power).
  5. Cool down: 10–15 minutes easy.
Method: Estimate CP from the weighted average of 3-minute and 9-minute mean power (mean × 0.9).
30-minute time trialJoe Friel
  1. Warm-up: 15 minutes easy.
  2. Test: 30 minutes all-out (settle in for the first 10 minutes, then hold the best sustainable effort for the last 20 minutes).
  3. Cool down: 10–15 minutes easy.
Method: Use the average power of the last 20 minutes as the CP/FTP estimate.
10K run test
  1. Warm-up: 15 minutes easy.
  2. Strides: 3–5 short strides (80–100 m, ~80% effort).
  3. Test: 10K all-out (best sustainable pace).
  4. Cool down: 10–15 minutes easy.
Method: Estimate from the mean power of an all-out 10K segment; if multiple segments exist, the best 10K segment is used.

FAQ

What is FTP?
FTP (Functional Threshold Power) is a practical estimate of the highest power you can sustain for about an hour. Cyclists use an FTP calculator to set power zones, pace threshold workouts, and track fitness. It is an empirical training number, not a laboratory measurement.
How does this FTP calculator estimate FTP from activity files?
Upload one GPX, FIT, or TCX file from a hard effort and choose the matching test protocol. The calculator reads the power stream and returns an FTP estimate. File-based estimation is the differentiator here; use a clean test ride when you can.
How do I use a 20-minute FTP test with this calculator?
Use the 30-minute time-trial protocol. After an easy warm-up, ride all-out for 30 minutes: settle in for 10 minutes, then hold your best sustainable power for the last 20 minutes. Upload that file and select the 30-minute TT protocol; the tool uses the last 20 minutes of mean power as the FTP estimate.
How does FTP relate to Critical Power?
FTP is an empirical threshold estimate. Critical Power is a model parameter fitted across multiple durations. They can be close, but they are not the same number. This FTP calculator estimates FTP from files or a 20-min test; use the Critical Power calculator when you want to fit CP and W' from MMP points.
Which file formats are supported?
GPX / FIT / TCX single-file upload is supported. If the file lacks power data or has poor recording quality, results may be unavailable or inaccurate.
Can I use the result to set training zones directly?
Use the FTP estimate as a starting point. Validate with repeated tests and day-to-day training feedback, and compare results using the same protocol and device setup.

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