Training Load Calculator

Turn a session's heart rate and duration into a Banister training impulse score, with a weekly total.

Sports and PaceUpdated 2026-10-214 min read

Training Load Calculator

Estimated maximum heart rate

...

Heart rate reserve...

Session load...

Weekly load...

Load per minute...

What it does

Training load is a way of putting one number on the work a session did. The best known version is the training impulse, or TRIMP, developed by Ivan Banister and described step by step in the training protocol published in BMJ Open. It weights the minutes of a session by how much of the available heart rate range the session used.

The heart rate reserve is the fraction of the gap between resting and maximum heart rate that the session covered. If your resting rate is 60 and your maximum is 190, then a session average of 160 sits 100 beats above resting on a range of 130, which is a reserve of about 0.77. That fraction goes into an exponential, so the weighting is not linear: the last part of the range counts for much more than the first part.

The published formula is TRIMPS equals the session duration in minutes times the heart rate reserve fraction times k, with k equal to 0.64 times e to the power of 1.92 times the reserve for men and 0.86 times e to the power of 1.67 for women. Those are the coefficients in the protocol, and they are why the same session gives a different number for a woman.

The maximum heart rate in the formula is usually taken as 220 minus the age, and that is the weak point of the whole method. The American College of Sports Medicine has said the age based estimate is no longer recommended, because it can be well off in either direction for an individual. A measured maximum heart rate is better, and the tool lets you work from the number that matters for you.

The score is only useful as a series. A single session tells you little, but a rise or a fall across weeks is the signal coaches look for, and the ratio between a recent week and the average of the last four weeks is the acute to chronic workload ratio that the workload literature uses to flag a spike.

How to use

Enter the sex, because the published coefficients differ.
Enter the age, which is used for the estimated maximum heart rate.
Enter your resting heart rate.
Enter the average heart rate across the session.
Enter the length of the session in minutes.
Enter how many sessions a week you do, then read the session and weekly load.

Formula

TRIMP for men = duration x reserve x 0.64 x e^(1.92 x reserve). TRIMP for women = duration x reserve x 0.86 x e^(1.67 x reserve). Reserve = (session heart rate - resting heart rate) / (maximum heart rate - resting heart rate), with maximum heart rate = 220 - age.

Reserve: Heart rate reserve fraction, the share of the rest to maximum range that the session used.
HRmax: Maximum heart rate, here estimated as 220 minus the age.
Duration: Length of the session in minutes.
TRIMP: Training impulse, in arbitrary units that are only comparable within one person.

The formula is stated for a single session with one average heart rate. Summing separate intervals with different heart rates is a segmented version of the model, and because the weighting is exponential it does not give exactly the same answer as applying the formula once to the session average. The load also only counts cardiovascular work, so strength work, sprints and mobility work need their own tracking.

Worked example

Example: a 30 minute session at 160 bpm for a 30 year old man

Defaults: male, 30 years old, resting heart rate 60, session average 160 bpm, 30 minutes and four sessions a week.

Estimated maximum heart rate: 220 - 30 = 190 bpm.
Heart rate reserve: (160 - 60) / (190 - 60) = 0.7692, which is 76.9%.
Weighting for men: 0.64 x e^(1.92 x 0.7692) = 2.804.
Session load: 30 x 0.7692 x 2.804 = 64.7 AU.
Load per minute: 64.7 / 30 = 2.156 AU per minute.
Four sessions a week gives 258.7 AU.
The tool shows 190 bpm, 76.9%, 64.7 AU, 258.7 AU and 2.156 AU per minute.

Reference table

Session load at 76.9% of the heart rate reserve, for a 30 year old man
Session length	Load	Load per minute
20 minutes	43.1 AU	2.156 AU
30 minutes	64.7 AU	2.156 AU
45 minutes	97.0 AU	2.156 AU
60 minutes	129.4 AU	2.156 AU
90 minutes	194.0 AU	2.156 AU

Limits

Uses an estimated maximum heart rate, and the age based estimate can be well off for an individual.
Needs a session average heart rate, so short bursts inside a steady session are smoothed away.
Scores only cardiovascular work, so lifting, sprints and mobility work are not counted.
The units are arbitrary, so a TRIMP number cannot be compared between two people.

Common mistakes

Entering the reserve as a percentage, so 76.9 instead of 0.769, which blows the exponential up.
Using the wrong coefficients for the sex, which changes the number for a reason that has nothing to do with the training.
Treating the load as an intensity rating, when it mixes duration and intensity and grows with both.
Comparing a TRIMP number with a zone based load, which are different scales entirely.
Ignoring a spike, because a load that is twice the recent average is the thing the ratio is there to catch.

Try it yourself

Quick checks. Answers sit tucked under each question.

What does the same session give for a woman?

The female weighting is 0.86 x e^(1.67 x 0.7692) = 3.108, so the session gives 30 x 0.7692 x 3.108 = 71.7 AU and the week gives 286.8 AU.

What does a 60 minute session at the same heart rate give?

The load per minute is 2.156 AU, so 60 minutes gives 129.4 AU and four sessions a week give 517.5 AU.

The resting rate drops from 60 to 55. What happens to the load?

The reserve rises from 0.7692 to 0.7778, and because the weighting is exponential the session load rises to 66.5 AU, up from 64.7.

Questions

What is a TRIMP score?

A measure of training load that weights the minutes of a session by the heart rate reserve you used. The published formula has different constants for men and women.

Why is 220 minus the age a problem?

Because the ACSM has said the age based estimate is no longer recommended: it can over or underestimate the real maximum, and the load scales with that maximum. A measured maximum heart rate is better.

Can I compare my score with somebody else's?

Not really. The score is scaled to your own heart rate range and your own resting rate, so it measures your work against your own capacity. Trends over time are the useful part.

What about interval sessions?

You can add the load of each interval separately, which is the segmented form of the model. It does not give exactly the same answer as one average heart rate for the whole session, because the weighting is exponential.

How do coaches use the weekly number?

They compare the recent week with the average of the previous weeks. A week that is much higher than the recent average is a spike, and the ratio of the two is the acute to chronic workload ratio used to flag when a training change is too big.

Does the score cover strength training?

No. TRIMP is a cardiovascular measure. Resistance work needs its own tracking, such as sets times reps times load, and the two are usually kept separate.

Sources

How this page was checked. The formula above was matched against the cited sources, and the worked example was run through the tool on this page before publishing. If you spot an error, contact us so we can fix it and note the correction.