Power capacity tool

FTP Calculator

Upload an activity file (GPX/FIT/TCX) to estimate Functional Threshold Power (FTP), Critical Power (CP), W', and running W/kg reference.

What does an FTP calculator estimate?

An FTP calculator estimates Functional Threshold Power, a practical power anchor for training zones and workout targets. In Trainingload.ai, uploaded GPX, FIT, or TCX activity data can also help estimate Critical Power, W', and running W/kg so threshold changes can be reviewed with training load.

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 3/9-minute, 30-minute TT, 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 CP, FTP, and W'

Use the estimate as a starting point, then compare it with repeat tests and day-to-day 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’s the difference between CP and FTP?
CP (Critical Power) is a model parameter related to your sustainable power ceiling, while FTP is often treated as an empirical threshold estimate. They can be close, but they are not guaranteed to be identical.
Why do different test protocols give different results?
Protocols emphasize different durations and energy systems, and are affected by pacing, fatigue, conditions, and device quality. Repeat the same protocol under similar conditions and use trends rather than single results.
Will my uploaded file be made public?
This tool analyzes the single activity file you upload to generate an estimate. Avoid uploading files that contain sensitive information. If privacy is a concern, export from a trusted platform and review the file before uploading.
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 it as a starting point. Validate with repeated tests and day-to-day training feedback, and compare results using the same protocol and device setup.

Turn estimates into better training decisions

Create an account to keep CP/FTP, workouts, and trends together, then review intensity distribution, track changes, and refine targets over time.

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FTP Calculator from Activity Files | Trainingload.ai