Training Stress Score Calculator

Training Stress Score (TSS) is a metric developed by Dr. Andrew Coggan that quantifies the physiological load of a training session relative to your functional threshold power (FTP) or threshold heart rate. A TSS of 100 represents a 1-hour maximal effort at threshold intensity.

For cycling: TSS = (Duration in seconds x Normalised Power x Intensity Factor) / (FTP x 3600) x 100. Intensity Factor (IF) = Normalised Power / FTP. A 1-hour ride at exactly FTP produces TSS = 100. A 2-hour ride at 0.85 IF produces TSS approximately 144.

Weekly TSS varies by athlete fitness and experience. A beginner might sustain 200 to 350 TSS per week. A trained amateur: 400 to 600. A competitive amateur: 600 to 900. A professional cyclist: 900 to 1500+. Individual capacity varies significantly; TSS is most useful for tracking your own trends over time.

Acute Training Load (ATL) is a 7-day exponentially weighted average of daily TSS, representing fatigue. Chronic Training Load (CTL) is a 42-day exponentially weighted average, representing fitness. Training Stress Balance (TSB) = CTL minus ATL, representing form or freshness. TSB of -10 to +5 is typical for hard training; +5 to +25 indicates peak readiness.

Yes. Heart rate-based TSS (hrTSS) uses the ratio of actual heart rate to threshold heart rate as a proxy for power. hrTSS = Duration(hrs) x HR ratio squared x 100, where HR ratio = average HR / threshold HR. This is less accurate than power-based TSS but provides useful trend data.