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TSS Calculator — Training Stress Score
Calculate Training Stress Score from normalised power, FTP and ride duration.
How We Calculate This
TSS Formula
TSS = (Duration in seconds x NP x IF) / (FTP x 3600) x 100
Where IF (Intensity Factor) = NP / FTP
This simplifies to: TSS = (Duration/3600) x IF^2 x 100
By definition, riding at exactly FTP for one hour produces a TSS of 100.
Frequently Asked Questions
Training Stress Score quantifies the training load of a ride on a 0-unlimited scale. A 1-hour ride at FTP = 100 TSS. It accounts for both intensity and duration.
Easy ride: 30-60 TSS. Moderate ride: 60-150 TSS. Hard ride: 150-250 TSS. Extremely hard: 250-400+ TSS. A Grand Tour stage can exceed 300 TSS.
Intensity Factor (IF) = Normalised Power / FTP. It represents how hard the ride was relative to your threshold. IF of 1.0 means you rode at exactly FTP on average.
TSS feeds into CTL (Chronic Training Load, your fitness) and ATL (Acute Training Load, your fatigue). Tracking these over time helps plan training and avoid overtraining.
Related Calculators
Training Stress Calculator
Calculate TSS (Training Stress Score) from power, duration, and FTP.
Power Zone Calculator
Calculate power-based training zones from your FTP.
Heart Rate Zone Calculator
Calculate heart rate training zones from max or threshold HR.
FTP Calculator
Estimate your Functional Threshold Power from test results.
Calorie Burn Calculator
Estimate calories burned cycling based on power, weight and duration.
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Last updated: June 2026
All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.