TSS calculator
Same formula as the Overload app
This TSS calculator computes Training Stress Score from normalized power and FTP, or from average heart rate and threshold heart rate, for any ride duration. Pick your method, enter the duration and either your power numbers or your heart rate numbers, and get the TSS along with intensity factor for the power method, the same figures Overload uses to track fitness and fatigue.
TSS
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A TSS of 100 corresponds to roughly one hour of riding right at your FTP.
How it works
TSS combines how hard a ride was with how long it lasted into a single number, defined by Allen and Coggan (Training and Racing with a Power Meter, 2010) as duration in hours times intensity factor squared times 100, where intensity factor is normalized power divided by FTP.
An hour at exactly FTP, intensity factor 1.0, always scores 100 TSS by definition, which is why 100 is the standard reference point for a hard, threshold-length effort.
When no power meter is available, the same score can be estimated from heart rate: average heart rate divided by LTHR, your lactate threshold heart rate, replaces intensity factor in the same formula. Heart-rate-based TSS is a rougher estimate since heart rate lags power and drifts with heat and fatigue.
Frequently asked questions
What is a normal TSS for a ride?
A recovery spin often lands under 50, a solid endurance ride around 100 to 150, and a hard interval session or race can push well past 150 in just an hour or two. Total TSS depends on both duration and intensity together, not either alone.
How is TSS different from intensity factor?
Intensity factor measures how hard an effort was relative to FTP, independent of how long it lasted. TSS multiplies that intensity by duration, so a short hard interval and a long steady ride can produce the same TSS despite feeling very different.
Can I calculate TSS without a power meter?
Yes, using average heart rate and your LTHR in place of normalized power and FTP, which this calculator supports directly. It's less precise than a power-based score because heart rate responds more slowly than power to changes in effort, especially during short, sharp intervals.
Related tools
- FTP zones calculatorCalculate your cycling FTP from a known value or a 20-minute power, free, with the seven Coggan training zones in watts.
- Watts per kg calculatorWork out your cycling power-to-weight ratio and rider category for free, using the Coggan power profile for men and women.
- Speed to power calculatorEstimate the power needed to hold a cycling speed, free, with gravity, rolling and aero components and a full speed table.
- Climb time calculatorPredict climb time, speed and VAM from length, elevation gain and power, free, with a table across a range of power outputs.
Overload computes TSS and fitness, fatigue and form
Overload calculates TSS automatically for every ride and tracks your fitness, fatigue and form over time. Free on iOS and Android.