TRIMP Training Load Calculator (Banister)

Understanding the TRIMP training load — concept and principle

TRIMP, short for training impulse, is a way to express the load of a workout as one number using only heart rate and time. It was introduced by Eric Banister for his fitness-fatigue model of performance and works for any endurance sport where you wear a heart rate monitor.

The exponential weight makes hard minutes count much more than easy ones.

How it is calculated

First the average heart rate is placed on your personal scale:

ΔHR = (average HR − resting HR) ÷ (maximum HR − resting HR)

Then:

Men: TRIMP = minutes × ΔHR × 0.64 × e^(1.92 × ΔHR)
Women: TRIMP = minutes × ΔHR × 0.86 × e^(1.67 × ΔHR)

ΔHR is the fraction of heart rate reserve used, between 0 (rest) and 1 (maximum). e ≈ 2.718.

The principle

Heart rate reserve makes intensity personal: 145 bpm means something different for a person with a resting rate of 50 and a maximum of 200 than for someone with 70 and 170. Multiplying duration by ΔHR alone would treat intensity as linear, yet blood lactate, a marker of physiological strain, rises roughly exponentially as heart rate approaches maximum. Banister therefore added an exponential weighting, with constants fitted to the lactate response of men and women. As a result, half an hour near maximum can count as much as a full hour at moderate effort.

Worked example

Male, 60 minutes, average 145 bpm, resting 60, maximum 185.

ΔHR = (145 − 60) ÷ (185 − 60) = 85 ÷ 125 = 0.68.
Weighting: 0.64 × e^(1.92 × 0.68) = 0.64 × e^1.3056 = 0.64 × 3.690 = 2.3615.
TRIMP = 60 × 0.68 × 2.3615 = 96.35.

Each point is the calculator re-run with only “Max HR” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Max HR	TRIMP
46.2	-0
92.5	15,229.77
139	329.25
185	96.35
231	49.43
278	31.78
370	17.82

How to read the result

TRIMP has no universal scale, so compare it with your own sessions. For the same man, 60 minutes at ΔHR 0.50 scores about 50, while 30 minutes at 0.90 scores about 97, almost the same as this hour. The female formula gives about 109 for the identical session. Track your weekly total and raise it gradually rather than in sudden jumps.

Common mistakes

Using an age-predicted maximum heart rate that is far from your real one.
Entering a resting heart rate measured during the day instead of on waking.
Comparing TRIMP values between people with different maximum and resting rates.
Using one average heart rate for stop-and-go sessions.

Keep in mind: Heart rate is affected by heat, dehydration, caffeine, illness and fatigue, so TRIMP is only an estimate of training load. It is not a medical assessment or diagnosis.

Frequently asked questions

Why does the formula differ for men and women?

Banister fitted the weighting to the typical blood lactate response, which differed between the sexes in the data he used.

What is the difference between Banister TRIMP and Edwards TRIMP?

Edwards' method multiplies minutes spent in five heart rate zones by weights from 1 to 5 instead of using an exponential curve.

Can I use TRIMP with a smartwatch?

Yes, the average heart rate and duration from a watch are enough, as long as your resting and maximum values are realistic.

Sources: Banister EW. Modeling elite athletic performance. In: MacDougall JD, Wenger HA, Green HJ, eds. Physiological Testing of the High-Performance Athlete. Human Kinetics, 1991. · Morton RH, Fitz-Clarke JR, Banister EW. Modeling human performance in running. J Appl Physiol 1990;69(3):1171–1177.

Checked 8 Nov 2026. Published formulas cited on the page. For information only — not medical advice.

Your numbers