Cycling Training Stress Score Calculator
Calculate TSS and Intensity Factor for any cycling ride from duration, average power, and FTP.
Includes weekly training load guidance for cyclists.
Training Stress Score (TSS) puts one number on the physiological cost of a ride.
Andrew Coggan devised it to combine duration and intensity in a single figure, since a flat-out hour and a gentle four hours are entirely different stimuli even though the longer ride burns more calories.
The formula runs in two steps:
- IF = average power ÷ FTP
- TSS = duration in hours × IF² × 100
FTP is Functional Threshold Power, the highest power you can hold for about an hour, and IF is the Intensity Factor, meaning how hard you rode relative to that threshold. An IF of 1.0 says you averaged exactly your FTP for the entire ride, which is brutal. Easy endurance rides land around 0.55 to 0.70, and a hard group ride might reach 0.85 to 0.90.
The squared term is the important part. Intensity counts twice over, so riding 10% harder costs you 21% more stress, while riding 10% longer costs exactly 10% more. That asymmetry is the whole argument for keeping easy days genuinely easy.
TSS is anchored so that one hour at exactly your FTP equals 100, by definition.
- A 1-hour ride at IF 0.75 gives 1 × 0.75² × 100 = 56
- A 3-hour ride at the same intensity gives 3 × 0.75² × 100 = 169
Recovering from a single ride
A rough guide to what one ride costs you, which is more useful day to day than any weekly total:
| Ride TSS | What to expect |
|---|---|
| Under 100 | Recovered by the next day |
| 100 to 200 | Some residual fatigue, fine to train through |
| 200 to 300 | Expect a day of reduced quality afterwards |
| Over 300 | Plan a genuine recovery day, or two |
Weekly totals
These are the TrainingPeaks and Coggan bands, and they apply to a whole week added together, not to one ride:
- Under 150: very light, a recovery or taper week
- 150 to 300: maintenance
- 300 to 450: a typical build phase for most riders
- 450 to 600: a high-volume or high-intensity block
- Over 600: extreme, and sustained weeks here are how people get injured or burnt out
Ramping matters more than the absolute number. Most coaches keep the week-on-week increase under about 10%, and a rider jumping from 300 to 500 in one week is asking for trouble regardless of where that lands on the table.
Note: this calculator uses average power as a proxy for normalized power (NP).
Normalized power accounts for the physiological cost of variable effort (sprints, hills, surges) and is typically 5-15% higher than average power on a hilly or dynamic ride.
If you have NP from your bike computer or training app, use that instead of average power for a more accurate TSS.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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