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Critical Power & W′ Calculator

Estimate your sustainable power ceiling and finite work capacity above it using evidence-based performance modeling.

About this calculator

Critical Power (CP) represents the highest power output you can sustain without continuous fatigue accumulation, while W′ describes your finite capacity for work performed above CP. Together, they provide a powerful framework for understanding high-intensity cycling performance.

This calculator estimates CP and W′ from maximal efforts and visualizes your power–duration relationship to help you design smarter intervals and pacing strategies.

Use two well-paced, maximal efforts of different durations, or multiple efforts for a more robust model fit.

Enter efforts and click Calculate to see results

What is Critical Power (CP)?
Critical Power represents the boundary between sustainable and unsustainable exercise intensity. When riding above CP, fatigue accumulates continuously, limiting how long the effort can be maintained.
What is W′?
W′ describes a finite amount of work that can be performed above CP. Once depleted, power output must fall to CP or below until recovery occurs.
How CP and W′ differ from FTP
FTP represents a practical training benchmark, while CP and W′ provide a more explicit performance model. Use CP/W′ alongside your FTP estimate for deeper insight.

Practical training applications

To translate CP and W′ into day-to-day workouts, use a clear zone framework.