TSS (Training Stress Score)

TSS is a single-number summary of a ride's training load, combining how hard it was and how long it lasted. An hour at FTP equals 100 TSS by definition. TSS is the unit that lets you compare a long easy ride to a short hard one and stack both into a weekly total.

TSS = (duration_s × NP × IF) / (FTP × 3600) × 100
    where IF = NP / FTP

TSS was developed by Dr. Andrew Coggan as part of the Performance Management Chart (PMC) framework. It lets coaches plan weeks by total load rather than time alone — a 60 TSS day is a 60 TSS day whether it came from 90 minutes of sweet spot or 3 hours of easy endurance.

Typical weekly TSS by training volume: 4–6 hrs/wk → 250–400; 8–10 hrs/wk → 500–700; 12–15 hrs/wk → 800–1100; and well above for WorldTour pros (often 1500+).