Calculate Training Stress Score (TSS) and Intensity Factor (IF) from your FTP, Normalized Power and ride duration.
Enter your actual Normalized Power if you know it (from your head unit or training platform). Average power is only a valid stand-in for a genuinely steady effort — for a variable ride, using average power will understate your real TSS. Don't have an FTP yet? Use the FTP Calculator first.
TSS is the standard single-number measure of a ride's training load, combining how hard the effort was relative to your threshold and how long it lasted. One hour at exactly your FTP is defined as 100 TSS — every other ride is scored relative to that reference point, which is what makes TSS comparable across very different rides.
This calculator uses the published Coggan/TrainingPeaks formula:
Intensity Factor (IF) expresses Normalized Power as a fraction of FTP — an IF of 1.0 means the ride averaged exactly threshold intensity (accounting for variability).
True Normalized Power comes from a continuous power recording — a 30-second rolling average, raised to the 4th power, averaged, then the 4th root taken — which weights hard surges more heavily than steady efforts at the same average watts. This calculator can't compute that from a single number, so it asks you to enter NP directly. If you don't have a true NP figure, average power is a reasonable stand-in only for a genuinely steady, flat effort; for a variable ride (climbing, surging, group riding), using average power will understate your real TSS.
Take a rider with a 250 W FTP holding 200 W Normalized Power for 90 minutes:
Enter your own FTP, Normalized Power and duration above to calculate your own TSS.
Allen & Coggan's Training and Racing with a Power Meter offers a commonly-cited rough guide to same-day recovery demand — treat it as orientation, not a rule, since actual recovery depends heavily on the individual and their training history:
TSS depends directly on an accurate FTP — if you haven't estimated yours yet, start with the FTP Calculator. Power Zones tell you how hard to ride during a workout; TSS tells you how much load that workout added afterward. See the Power Zones Calculator for the training-zone side of the same FTP number.
This calculator implements the published Coggan/TrainingPeaks TSS model exactly, from Allen, H. & Coggan, A. (2010), Training and Racing with a Power Meter (2nd ed.), VeloPress, and Coggan, A.R., "Normalized Power, Intensity Factor and Training Stress Score," TrainingPeaks. No coefficients are invented here — the only modeling choice is that this calculator takes Normalized Power as a direct input rather than computing it from a power file, which it has no way to do from simple numeric inputs alone (see "Normalized Power vs average power" above).
