Banister TRIMP & Target Session Calculator
Calculate a completed session’s Banister TRIMP from active time and average heart rate, or plan the duration or average heart rate that mathematically reaches a target load.
Session TRIMP100.44
- Heart-rate reserve used
- 69.23%
- Intensity weighting factor
- 2.42
- TRIMP per hour
- 100.44
- Feasibility check
- The entered average heart rate is at least resting heart rate and no greater than maximum heart rate.
TRIMP is an arbitrary-unit workload estimate based on average heart rate and active duration.
How to use this calculator
- Choose whether you are calculating a completed session, required duration, or required average heart rate.
- Select the Banister coefficient profile you want to use consistently for your own records.
- Enter active exercise time and heart rates measured for the activity, not pauses or recovery time.
- Enter a target TRIMP for either reverse-planning mode, then read the feasibility check before using the result.
How Banister TRIMP is calculated
Banister training impulse, usually called TRIMP, combines active exercise time with relative heart-rate intensity. It first expresses average exercise heart rate as heart-rate reserve: r = (H − Hr) ÷ (Hm − Hr), where H is average exercise heart rate, Hr is resting heart rate, and Hm is maximum heart rate.
The session calculation is Q = t × a × r × e^(b × r). Here t is active minutes and Q is TRIMP in arbitrary units. The historical male profile uses a = 0.64 and b = 1.92; the female profile uses a = 0.86 and b = 1.67. The exponential term means a higher average heart rate increases the load more than proportionally.
Planning from a target load
For a target duration, the calculator divides the target TRIMP by the load accumulated per minute at the entered average heart rate: t = Q ÷ (a × r × e^(b × r)). An average heart rate equal to resting heart rate has a reserve fraction of zero, so it cannot accumulate a positive target TRIMP in this model.
For a target average heart rate, the calculation reverses the exponential expression with the principal Lambert W function: r = W(b × Q ÷ (t × a)) ÷ b, then H = Hr + r × (Hm − Hr). The result is rejected when the solved reserve is outside zero to one, because that would require a heart rate outside the entered resting-to-maximum range.
What changes the result most
Duration changes TRIMP in direct proportion. Average heart rate can have a larger effect near the top of the entered range because it changes both heart-rate reserve and the exponential weighting. Resting and maximum heart rates also matter: changing either changes the reserve fraction assigned to the same exercise heart rate. Compare sessions only when those values and the coefficient profile are held consistent.
What this calculation leaves out
This is an average-heart-rate model. It can understate short intervals, sprints, resistance training, heat stress, fatigue, and any session where heart rate lags behind muscular effort. It does not estimate calories, recovery time, fitness, injury risk, or whether a mathematically possible intensity is appropriate for you.
Worked example
With the male coefficients, a 60-minute session at an average of 150 bpm, a resting heart rate of 60 bpm, and a maximum heart rate of 190 bpm has r = (150 − 60) ÷ (190 − 60) = 0.6923. Its weighting factor is 0.64 × e^(1.92 × 0.6923) = 2.4180, producing 60 × 0.6923 × 2.4180 = 100.44 TRIMP.
At the same heart rate, a target of 100 TRIMP requires 59.74 active minutes. Holding the duration at 60 minutes instead, the reverse calculation gives an unrounded average heart rate of 149.83 bpm, which the calculator displays as 150 bpm.
Common questions
What is Banister TRIMP?
Banister TRIMP is a heart-rate-based estimate of training load in arbitrary units. It combines active duration with heart-rate reserve and applies an exponential weight so that higher-intensity work counts more heavily. It is most useful for comparing a person’s own aerobic sessions measured in a consistent way.
How do I calculate TRIMP from average heart rate?
Subtract resting heart rate from average exercise heart rate, then divide by maximum minus resting heart rate to obtain heart-rate reserve. Multiply active minutes by that fraction and the appropriate Banister exponential weighting factor. This calculator performs those steps after checking that the entered heart rates are in a possible order.
How long must I train to reach a target TRIMP?
Divide the target TRIMP by the TRIMP per minute at your chosen average heart rate. A higher average heart rate reduces the required time because the Banister weighting rises exponentially. The answer is active exercise time, not elapsed time including rests or pauses.
What average heart rate corresponds to a target TRIMP?
For a fixed duration, the calculator solves the Banister equation using the principal Lambert W function and converts the result back to bpm. If the solution is above your entered maximum heart rate, the target is infeasible for that duration and the calculator says so. A mathematical equivalent is not an intensity prescription.
Why does Banister TRIMP use different coefficient profiles?
The original Banister model published separate population-level curves with different constants for males and females. They describe historical group relationships between heart-rate reserve and lactate response; they are not individualized physiological tests. Choose one profile and keep it unchanged when comparing your own trend over time.
Is TRIMP the same as TSS, cardio load, or calories?
No. TRIMP is a heart-rate-based training-load estimate, while TSS-style measures usually use power or pace relative to a threshold, and device cardio-load scores may use proprietary methods. Calories estimate energy expenditure, which is a different question. Values from these systems are not directly interchangeable.