About the Training Stress Score Calculator
Training Stress Score (TSS) puts a single number on how hard a workout was, combining duration and intensity relative to your threshold. By definition, one hour at your functional threshold power (FTP) scores 100 TSS. This calculator works it out three ways: from normalized power and FTP for cycling, from average heart rate and lactate-threshold heart rate, or from running pace against your threshold pace.
Cyclists, triathletes and runners use TSS to track training load over time, plan recovery and build structured weeks without overreaching. Alongside TSS you get the intensity factor (IF) — how hard the session was compared with threshold — plus a rough guide to how long recovery usually takes and a chart showing how TSS grows with duration at the same intensity.
Power-based TSS is the original and most precise method. The heart-rate version here normalises Banister’s TRIMP so an hour at threshold heart rate equals 100, and the pace version squares the pace-based intensity. Both are estimates, best used for consistent tracking rather than exact comparison with power data.
With the default inputs, the training stress score is 96. Change any value above to recalculate instantly.
How to use the training stress score calculator
- 1Choose whether to calculate from power, heart rate or running pace.
- 2Enter the workout duration in hours and minutes.
- 3Enter normalized power and FTP, or heart-rate values, or your workout and threshold paces.
- 4Read TSS, intensity factor and the recovery guide.
- 5Add up TSS across the week to track your overall training load.
Formula and method
Power-based TSS, developed by Andrew Coggan, compares normalized power with FTP. Because IF = NP ÷ FTP, the formula simplifies to hours × IF² × 100, so an hour at FTP scores exactly 100 and intensity counts more than duration. For running pace, IF is threshold pace ÷ workout pace (in seconds) and the same hours × IF² × 100 rule is applied.
The heart-rate method uses Banister’s TRIMP: minutes × ΔHR × 0.64e^(1.92ΔHR) for men (0.86e^(1.67ΔHR) for women), where ΔHR is the fraction of heart-rate reserve. Dividing the workout TRIMP by the TRIMP of one hour at lactate-threshold heart rate and multiplying by 100 puts it on the TSS scale. Recovery guidance follows the commonly used bands from Allen and Coggan: under 150, 150–300, 300–450 and over 450.
- NP
- Normalized power (W)
- FTP
- Functional threshold power (W)
- IF
- Intensity factor, intensity relative to threshold
- ΔHR
- (HR − resting HR) ÷ (max HR − resting HR)
Worked examples
90-minute ride at 200 W NP with a 250 W FTP
IF = 200 ÷ 250 = 0.80. TSS = 5,400 × 200 × 0.8 ÷ (250 × 3,600) × 100 = 96, the same as 1.5 h × 0.8² × 100.
1-hour run at 150 bpm (LTHR 170, rest 50, max 190), male
ΔHR = (150 − 50) ÷ 140 = 0.714 and threshold ΔHR = 120 ÷ 140 = 0.857. TRIMP for the run is 60 × 0.714 × 0.64e^(1.92×0.714) ≈ 108.1 versus 170.7 for an hour at threshold, so hrTSS ≈ 63 (an equivalent IF of about 0.80).
50-minute run at 5:00 pace with a 4:30 threshold pace
IF = 270 s ÷ 300 s = 0.90. TSS = 50/60 h × 0.9² × 100 = 67.5.
Frequently asked questions
What is a good TSS for a workout?+
It depends on your goals and fitness. Easy rides and runs often score 30–70, a solid 2-hour endurance session around 100–150, and long races or big days can exceed 250–300. One hour at threshold is always 100.
What is intensity factor?+
Intensity factor (IF) is how hard the session was relative to threshold: normalized power divided by FTP. An IF of 0.75 is a steady endurance effort, around 0.9 is tempo or sweet spot, and 1.0 is a full threshold effort.
How much TSS per week should I do?+
Recreational cyclists and triathletes often train at 200–400 TSS per week, while serious amateurs may sustain 500–800 and professionals more. Increase weekly load gradually and include easier recovery weeks.
Is heart-rate TSS as accurate as power TSS?+
No. Heart rate lags behind effort, drifts upward with heat and fatigue, and misses short hard efforts, so hrTSS is a rougher estimate. It is still useful for tracking trends when you train consistently with the same method.
Why does my TSS differ from my app?+
Apps calculate normalized power from second-by-second data, may use graded pace for runs, and sometimes use different heart-rate models. Using average power instead of NP also gives a lower score, especially for variable rides.