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TSS CALCULATOR

Ride duration, power, and FTP in. Training Stress Score out.

hours
minutes

Average power works fine for steady efforts. For variable rides, NP is more accurate.

METHODOLOGY

Formula:TSS = (Duration in seconds x NP x IF) / (FTP x 3600) x 100, where IF (Intensity Factor) = NP / FTP. One hour at FTP equals exactly 100 TSS — that's the anchor point.

Origin: TSS was developed by Dr. Andrew Coggan and Hunter Allen as part of the performance-management framework built into TrainingPeaks and WKO software. It quantifies the physiological cost of a ride in a single number you can track over time.

NP vs Average Power: Normalised Power accounts for the variability of effort — hard surges cost more metabolically than the same average watts held steady. If your ride had significant variation (crits, group rides, hilly routes), NP gives a more accurate TSS. For steady-state efforts (time trials, indoor sessions), average power and NP are nearly identical.

Limitations:TSS treats all stress below threshold equally and doesn't capture the disproportionate metabolic cost of time spent above threshold. It doesn't factor in environmental load — heat, altitude, and humidity add physiological stress that TSS ignores. And it requires accurate power data; heart-rate-derived TSS (hrTSS) is a rougher estimate.

Last updated: July 2026 · Tool version 1.0

FROM HERE

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