Critical Power & W′ Calculator

Critical Power (CP) is the highest power you can hold in a metabolic steady state — conceptually close to FTP, but modelled from your actual maximal efforts rather than a single test.

W′ (‘W-prime’) is your anaerobic battery: the fixed amount of work you can do above CP before you have to back off. It's what you spend on attacks, short climbs and sprints, and it recharges when you drop back below CP.

Give two honest maximal efforts of different lengths — for example a 3-minute and a 12-minute — and the two-parameter model solves for both CP and W′.