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Training Stress Calculator (TSS)
Calculate TSS from power, duration, and FTP.
How We Calculate This
Power TSS = (Duration in seconds × NP × IF) / (FTP × 3600) × 100, the model defined by Dr Andrew Coggan. Normalised Power (NP) accounts for intensity variability and Intensity Factor (IF) = NP / FTP. If only average power is available, it is used in place of NP. One hour at FTP equals 100 TSS.
Heart-rate TSS estimates intensity from heart-rate reserve (Karvonen): IF = (average HR − resting HR) / (threshold HR − resting HR), then TSS = hours × IF² × 100. This anchors easy rides correctly instead of inflating them with a raw average-to-threshold ratio.
RPE TSS maps your session effort (Borg CR10) to an approximate IF and uses the same hours × IF² × 100 form. Use power when you have it — it is the most accurate.
Frequently Asked Questions
A typical endurance ride produces 50-100 TSS. Hard interval sessions are 80-150 TSS. Long sportives may be 200-400 TSS. Weekly totals of 300-600 TSS are typical for recreational cyclists training consistently.
IF is the ratio of normalised power to your FTP. An IF of 1.0 means you rode at threshold. Below 0.75 is endurance, 0.75-0.90 is tempo, and above 1.05 is VO2max or above.
Heart rate-based TSS (hrTSS) is less accurate than power-based TSS because heart rate responds slowly to effort changes and is affected by cardiac drift, heat and fatigue. This calculator derives intensity from heart-rate reserve (average HR, resting HR and threshold HR) so easy rides are not overstated, but use power data when available for the most precise tracking.
Increase weekly TSS by no more than 5-10% per week. For most recreational cyclists, 300-500 TSS per week is sustainable. Elite riders may accumulate 800-1200 TSS per week during heavy training blocks.
Related Calculators
TSS Calculator
Calculate Training Stress Score from power and duration.
Power Zone Calculator
Calculate power-based training zones from your FTP.
FTP Calculator
Estimate your Functional Threshold Power from test results.
Heart Rate Zone Calculator
Calculate heart rate training zones from max or threshold HR.
Ramp Test Calculator
Calculate FTP from a ramp test result.
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Last updated: March 2026
All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.