The TRIMP Training Load Calculator is a free online tool that measures how much stress a session placed on your heart, using its duration and your heart rate, in the form of a TRIMP score that rises with both time and effort. It runs fully in your browser, needs no sign-up, and gives you a clear result in seconds, so you can use it at the track, in the gym, or at home without installing anything or sharing personal data.
This tool works from simple numbers you already know or can measure in one session. You enter the session duration in minutes, your average heart rate, your resting heart rate, and your maximum heart rate, all in beats per minute. The tool then applies a standard formula to those numbers, so the result follows the same maths every time and two people who enter the same inputs always get the same output.
Your result shows a TRIMP score for the session, where longer sessions and higher average heart rates both push the number higher. Read the main number first, then look at the extra figures, because they often explain the result better than a single score alone. A result that looks odd usually points to a typing error or a unit mix-up, so check your inputs before you trust an extreme value.
Here is a worked example to make the maths concrete. In this example, sixty minutes at an average of 150 beats per minute, with a resting rate of 60 and a maximum of 190, gives a TRIMP near 100, which is a solid moderate-to-hard session. Try the same numbers in the tool yourself, then change one input at a time, and watch how the result moves, because that habit teaches you far more than reading a formula on its own.
How should you read the result in practice? In general, low scores mean easy sessions, middle scores mean steady training, and high scores mean long or intense work that should be followed by easier days. Use the result to compare your own tests over time, not to judge yourself against strangers online, because age, sport, training history, and test conditions all change what a good number looks like for you.
To get the most from this tool, follow a few simple habits. First, measure resting heart rate first thing in the morning, use the same heart rate monitor each time, and compare scores only for similar sports and session types. Second, test under similar conditions each time, with the same warm-up and the same course or equipment, so changes in the number reflect changes in your fitness rather than changes in the test itself.
Watch out for common mistakes, because small errors can move the result a lot. The most frequent problem is using a guessed maximum heart rate that is far too high or too low, because the whole score depends on the gap between your resting and maximum rates. A second common problem is entering numbers in the wrong units, for example minutes instead of seconds, or pounds instead of kilograms, so double-check the unit labels on every field.
Finally, keep the limits of this tool in mind. In short, this tool estimates load from heart rate only, so it misses strength work, heat, illness, and poor sleep, all of which can make a session feel harder than the number shows. Used with that care, this free tool becomes a practical part of your training routine, giving you honest numbers you can track week after week without cost, accounts, or complicated software.
If you test regularly, keep a simple log with the date, your inputs, and your result, because a short written record shows progress far better than memory alone. Review the log once a month, look for slow steady improvement rather than daily jumps, and adjust your training only when a pattern holds for several weeks, not after a single unusual test.
Version en espanol: Calculadora de Carga TRIMP – Para Deportistas y Entrenadores