Training Stress Score (TSS) Calculator

About this calculator

Training Stress Score (TSS) is a proprietary metric created by Dr. Andrew Coggan and popularized through TrainingPeaks and power-meter-based cycling coaching, designed to quantify the overall physiological stress of a single ride in one number. It combines duration, Normalized Power (NP) — a weighted-average power output that accounts for the variability of real-world riding better than a simple average — and your FTP (Functional Threshold Power), the highest power you can sustain for roughly an hour. The formula is TSS = (seconds × NP × IF) / (FTP × 3600) × 100, where IF (Intensity Factor) is NP divided by FTP.

Cyclists, triathletes, and their coaches use TSS as the core building block of periodized training plans: a 1-hour ride at exactly FTP scores 100 TSS by definition, giving athletes a consistent yardstick to compare a short hard interval session against a long easy endurance ride. TSS feeds directly into longer-term load-management metrics like CTL (Chronic Training Load, or ‘fitness’) and ATL (Acute Training Load, or ‘fatigue’), which coaches track to manage the balance between building fitness and avoiding overtraining or injury.

This calculator takes your ride duration, normalized power, and FTP, and returns the TSS for that ride so you can log it against your training plan.