Free tool · No signupTSS, intensity factor and recovery

TSS Calculator for Cycling

One hour at your FTP is 100 TSS. Enter how long you rode, your normalized power and your FTP to get your Training Stress Score and intensity factor. Don’t know your FTP? Start with the FTP calculator.

Your ride
h
min
W
W
Training stress
102TSS
LowUsually recovered by the next day.
Intensity factor (IF)0.83
TSS per hour68
One hour at FTP100
Get TSS for every ride automatically

WattsUP works out TSS for each workout and imported ride and adds it to your fitness and fatigue curve.

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What TSS measures

Training Stress Score puts a single number on how hard a ride was for you, combining how long you rode with how intense it was relative to your FTP. Hunter Allen and Andrew Coggan introduced it so that a long easy ride and a short hard one can be compared on the same scale.

Because it is relative to your FTP, the same ride gives a stronger rider a lower score. That is also why your FTP needs to be current: an FTP that is set too low makes every ride look harder than it was.

The formula

  1. Intensity factor: IF = normalized power ÷ FTP.
  2. TSS: (seconds × NP × IF) ÷ (FTP × 3600) × 100.
  3. Example: 90 minutes at 190 W NP with a 230 W FTP gives IF 0.83 and about 102 TSS.

Want TSS added up over weeks? The training load modeler shows how daily TSS becomes fitness, fatigue and form, and CTL, ATL and TSB explained covers what the numbers mean.

Frequently asked questions

How is TSS calculated?+

TSS = (seconds × NP × IF) ÷ (FTP × 3600) × 100, where NP is normalized power and IF (intensity factor) is NP divided by FTP. Riding exactly at FTP for one hour scores 100.

Can I calculate TSS from average power?+

You can get an estimate, but it will usually be too low. Normalized power weights hard surges more heavily, so for rides with hills, sprints or stops, NP is higher than average power. On a steady trainer ride the two are close.

What is a good TSS for a ride?+

There is no single good number: it depends on your training load. As a rough guide from Allen and Coggan, under 150 is low and usually recovered from by the next day, 150–300 is medium, 300–450 is high, and over 450 means several days of fatigue.

What is intensity factor (IF)?+

IF is normalized power divided by FTP. An easy endurance ride is often around 0.65–0.75, a hard group ride 0.85–0.95, and a one-hour all-out time trial close to 1.0.

How does TSS relate to fitness and fatigue?+

Your daily TSS feeds two rolling averages: chronic training load (CTL, roughly 42 days, “fitness”) and acute training load (ATL, roughly 7 days, “fatigue”). The difference between them is training stress balance (TSB, “form”).

Sources

Recovery bands are an approximate guide from Allen and Coggan’s Training and Racing with a Power Meter (VeloPress, 2010).

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