TSS stands for Training Stress Score, a metric that measures the total workload of a cycling session.
It combines intensity and duration into a single number to show how much stress the workout placed on your body.
The higher the TSS, the more demanding the session was.
TSS is based on your Functional Threshold Power (FTP), which represents the effort you can sustain for about an hour.
A ride at FTP for exactly one hour equals 100 TSS.
More precisely, TSS is calculated using Normalized Power (NP) — not average power — along with your FTP and ride duration. NP adjusts for the variability of real-world riding, which is why two rides with the same average watts can produce very different TSS values.
Lower-intensity, longer rides and short, intense efforts can result in similar TSS scores, but with different physiological effects.
This metric helps track fatigue, manage weekly load, and plan recovery.
It’s commonly used in training software to monitor performance and avoid overtraining.
TSS also helps compare different types of workouts and understand their impact on your fitness.
By analyzing TSS over time, you can build a more balanced and effective training plan.
Understanding TSS is key to training smarter, not just harder.
The TSS formula and how to read your numbers
TSS is calculated from three inputs: the duration of the ride in seconds, your Normalized Power for the ride, and the Intensity Factor, which is your NP divided by your FTP. The full formula is TSS = (duration in seconds × NP × IF) / (FTP × 3600) × 100. In practice you rarely calculate this by hand, since training platforms compute it automatically, but knowing the inputs explains why a hard, variable ride scores higher than a steady one of the same length.
Once you have a score, the value is in reading it against your own load. As a rough guide for a single session:
| TSS | Session type | Typical recovery |
|---|---|---|
| Under 150 | Easy to moderate | Fresh by the next day |
| 150 to 300 | Moderate to hard | Some residual fatigue the next day |
| 300 to 450 | Hard, long ride | Lingering fatigue for two days |
| Over 450 | Very demanding | Several days to absorb |
These ranges are guidelines rather than rules, since recovery depends on your fitness, sleep, and nutrition. The real power of TSS comes from tracking it over weeks to balance training stress against recovery.
That is what CTL, chronic training load does: it averages your daily TSS over 42 days to represent fitness, alongside ATL over 7 days for fatigue and TSB, the difference between the two, for form. Raising it has its own arithmetic, worked through in how to increase CTL.