Power capacity tool

Critical Power Calculator

Use MMP points to fit CP and W', and derive Pmax and eFTP.

CRITICAL POWER

PMAX

eFTP

What is Critical Power?

Critical Power (CP) is a modeled sustainable power reference. Work above CP draws from W', so reliable 3-20 minute MMP points usually produce a more useful CP/W' estimate than sprint-only data. Use CP with training load and workout quality before changing zones.

Calculator

Paste your best power (watts) for common durations and choose which points to include.

Inputs

Enter MMP (max mean power) values. Toggle which points are used for CP/W' fitting.

MMP Points

1s MMP (W)

5s MMP (W)

1m MMP (W)

3m MMP (W)

5m MMP (W)

12m MMP (W)

20m MMP (W)

Tip: enable at least two points ≥ 3 minutes for fitting.

Model: linear work-time fit (P·t vs t). CP is the slope and W' is the intercept. Treat results as estimates and validate with repeatable tests.

Results

Select at least two valid points to see results.

Add MMP values (watts) and enable at least two ≥ 3-minute points.

Explained

What these outputs represent in training terms.

Your sustainable power ceiling from the model fit. Used as a reference for long intervals and endurance zones.

Your finite work capacity above CP, expressed as an energy-like number (kJ). It influences repeatability of hard efforts.

Pmax

A practical peak power proxy from your short-duration best power. Useful for sprint/anaerobic context.

eFTP

Estimated FTP from 20-minute power when available, otherwise based on CP.

How to use the Critical Power calculator

Collect quality power points

Use recent max mean power values, especially 3-20 minute efforts, recorded with the same power source when possible.

Select points and calculate

Toggle the efforts you trust for CP/W' fitting, then review CP, W', Pmax, and eFTP together.

Validate before changing zones

Treat the result as a model estimate. Compare it with workouts, repeatable tests, and fatigue before updating training targets.

FAQ

Which durations should I use?

For CP/W' fitting, prioritize longer efforts (3–20 min). Short durations (1–60s) are useful for Pmax, but are often too noisy for CP fitting.

Why can CP differ from FTP?

CP comes from a model fit across multiple durations, while FTP is often an empirical threshold estimate (e.g., 20-minute test). They can be close but not always identical.

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Bring CP/FTP into long-term analysis: zones, fatigue, and trends.

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