TSS Calculator
Training Stress Score and Intensity Factor from duration, Normalized Power and FTP.
What TSS is and why it matters
TSS (Training Stress Score) is a single measure of training load that combines both duration and intensity. One hour ridden exactly at FTP equals 100 TSS. Summing TSS across a week lets you manage fitness and recovery: sudden jumps in weekly load are the best predictor of overtraining and injury.
The formula
TSS = (seconds × NP × IF) / (FTP × 3600) × 100, where IF = NP / FTP. Intensity Factor shows how hard the session was relative to your threshold: recovery rides sit at 0.5–0.65, tempo at 0.75–0.85, a time trial at 0.95–1.05. For steady rides, average power is an acceptable substitute for NP.
Frequently asked questions
How much TSS per week is normal?
Recreational athletes typically accumulate 300–500 TSS per week, ambitious age-groupers 500–700, professionals 700–1000+. The ramp matters more than the number: avoid increasing weekly TSS by more than ~10% at a time.
How is NP different from average power?
Normalized Power weights surging efforts: short hard accelerations cost the body more than the average suggests. On steady rides NP ≈ average power; in group rides or hilly terrain NP is noticeably higher.
Can I compute TSS for running and swimming?
Yes — analogues exist: rTSS from pace for running and sTSS for swimming. This calculator computes the classic power-based TSS; for running, use your threshold pace in our zones generator.