Free tool · Training load
TRIMP calculator
Short answer
TRIMP (training impulse) scores a session from its duration and how much of your heart rate reserve it used, weighted so harder minutes count for more: minutes × ratio × 0.64e^(1.92 × ratio) for men. A 45-minute session averaging 150 bpm, with a resting heart rate of 55 and a max of 185, uses 73% of reserve and scores about 86 (men's weighting) or 96 (women's).
Last reviewed 27 October 20262 published sourcesNot medical advice
Reps keeps track of this for you on iPhone, iPad and Apple Watch.
Get Reps freeTRIMP calculator
Use the session's average heart rate from your watch, and your own resting and max heart rate if you know them.
Enter the session's length and average heart rate, plus your resting and max heart rate.
Runs entirely in your browser. Nothing you type is saved or sent anywhere.
| Average heart rate | Reserve used | Men | Women |
|---|---|---|---|
| 110 bpm | 42% | 27 | 33 |
| 130 bpm | 58% | 50 | 59 |
| 150 bpm | 73% | 86 | 96 |
| 165 bpm | 85% | 124 | 135 |
| 180 bpm | 96% | 175 | 185 |
Where the formula comes from
Banister's training impulse multiplies the minutes of a session by the fraction of heart rate reserve it used and by a weighting that grows exponentially with intensity: 0.64e^(1.92x) for men and 0.86e^(1.67x) for women (Morton et al., 1990). The weighting follows how blood lactate rises with exercise intensity, so a minute near your max counts far more than an easy one.
Heart rate reserve is your max minus your resting heart rate, the same reserve Karvonen's training zones are built on (Karvonen et al., 1957). Set your zones with the heart rate zones calculator, score sessions by feel with the training load calculator, or see how fast your load is rising with the ACWR calculator.
Training load, counted for you
Reps tracks how hard each workout was from your Apple Watch heart rate and shows whether your load is building, holding or easing off.
Free to download · iPhone, iPad and Apple Watch
Common questions
What is a good TRIMP score?
There isn't a universal one. TRIMP is in arbitrary units and depends on your heart rates, so it is only meaningful against your own sessions. Watch how your weekly total changes.
Why are men's and women's TRIMP different?
The weighting curve differs: 0.64e^(1.92x) for men and 0.86e^(1.67x) for women, where x is the share of heart rate reserve used. The same session therefore scores a little differently.
Is TRIMP better than session RPE?
They measure different things: TRIMP uses heart rate, session RPE uses how hard it felt. Heart rate misses effort in short sprints and heavy lifting, so many people use RPE for strength work and either one for steady cardio.
Sources
Figures on this page were checked against these publications on 27 October 2026.
- Morton RH, Fitz-Clarke JR, Banister EW. Modeling human performance in running. Journal of Applied Physiology. 1990;69(3):1171–1177. doi.org/10.1152/jappl.1990.69.3.1171
- Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Annales Medicinae Experimentalis et Biologiae Fenniae. 1957;35(3):307–315. pubmed.ncbi.nlm.nih.gov/13470504/
More recovery and training load tools
- ACWR calculatorAcute:chronic workload ratio from four weeks of load, with the sweet spot and its caveats.
- HRV baseline calculatorA log-based 7-day HRV average, your normal range and day-to-day variation.
- Training load calculatorWeekly session-RPE load, monotony and strain from how hard each session felt.
- Resting heart rate by ageSee where your resting heart rate falls among people your age and sex, using national NHANES percentiles.