TSS Calculator

Not all hours of training are equal. A gentle hour and a brutal hour both take sixty minutes, but they cost your body very different amounts. Training Stress Score puts a number on that cost, so you can compare sessions, balance your week, and avoid the trap of measuring training by time alone. The calculator above works it out.

How TSS is built

TSS combines two things: how long you trained and how hard. The intensity comes from your normalized power relative to your FTP, a ratio called the intensity factor. Square that intensity, multiply by the duration, and scale it, and you get TSS.

The anchor point is simple to remember. One hour ridden right at threshold, an intensity factor of 1.0, equals 100 TSS. An easier hour scores less. A shorter but harder effort can score the same as a longer easy one, which is exactly the point: it captures cost, not just clock time.

Enter your session duration, your normalized or average power, and your current FTP. The calculator returns your TSS and your intensity factor, plus a rough sense of how much recovery the session demands.

Using it to balance your week

TSS shines as a planning tool. By tracking the total across a week you can see whether you are building load sensibly or spiking it in a way your body cannot absorb. A steady, gradual rise in weekly TSS is how fitness is built. Sharp jumps are how injuries and burnout arrive.

It also stops the most common self-coaching mistake: piling hard session on hard session because each one alone felt fine. The weekly total tells the truth your legs sometimes hide.

Keep your FTP honest

TSS is only as good as the FTP it is built on. A stale or inflated FTP throws every score off. Retest every four to six weeks so your numbers stay real. For the full picture of how TSS, intensity, and load fit together, read the training stress score guide.