TRIMP Training Impulse Calculator
Training impulse, or TRIMP, condenses a heart-rate session into a single training-load number by combining how long you trained with how hard you trained. The Banister exponentially weighted formula multiplies session duration by your fractional heart rate reserve and an exponential weighting that rises with intensity, so a hard session accumulates load far faster than an easy one of the same length. This calculator takes session duration, average exercise heart rate, resting and maximum heart rates, and sex, then returns the TRIMP score along with the fractional heart rate reserve and the weighting factor used. Enter a measured maximum heart rate where possible for the most accurate result.
Banister TRIMP formula
fractional HR reserve = (exercise HR - resting HR) / (maximum HR - resting HR)
weighting factor = 0.64 * e^(b * fractional HR reserve), b = 1.92 male, 1.67 female
TRIMP = duration (min) * fractional HR reserve * weighting factor
TRIMP per minute = TRIMP / duration
Worked example: 45 min, exercise HR 150, resting 60, maximum 190, male. Reserve = (150 - 60)/(190 - 60) = 0.6923. Weighting = 0.64 * e^(1.92*0.6923) = 2.4191. TRIMP = 45 * 0.6923 * 2.4191 = 75.36.
TRIMP notes
- The exponential weighting makes hard sessions count for disproportionately more load.
- The coefficient b differs by sex: 1.92 for men, 1.67 for women.
- Enter a measured maximum heart rate where possible; age formulas are estimates.
- Sum daily TRIMP to track weekly load or feed fitness-fatigue models.
- TRIMP puts sessions of different length and intensity on one comparable scale.
TRIMP: frequently asked questions
What is TRIMP?
TRIMP, or training impulse, is a single number that combines how long a session lasted with how hard it was, based on heart rate. The Banister exponentially weighted version multiplies session duration by the fractional heart rate reserve and an exponential weighting factor, so harder sessions count for disproportionately more.
What is the Banister TRIMP formula?
TRIMP equals duration in minutes times fractional heart rate reserve times 0.64 times e to the power of (b times fractional heart rate reserve), where b is 1.92 for men and 1.67 for women. Fractional heart rate reserve equals (exercise heart rate minus resting heart rate) divided by (maximum heart rate minus resting heart rate).
Why is the weighting exponential?
The exponential term reflects the rising blood lactate response at higher intensities. It means a session at high heart rate accumulates TRIMP much faster than a longer session at low heart rate, capturing the greater physiological strain of hard efforts.
What inputs do I need?
Enter session duration in minutes, your average exercise heart rate, your resting heart rate, your maximum heart rate, and your sex. Sex selects the weighting coefficient. Maximum heart rate is a user-editable input so you can enter a measured value or an age-based estimate.
How is TRIMP used?
TRIMP quantifies the load of each session so loads can be summed across a week, compared between sessions, or fed into models of fitness and fatigue. It turns heart-rate sessions of different lengths and intensities onto one comparable scale.
Official sources
- National Center for Biotechnology Information (PubMed): Banister TRIMP and training-load literature.
- American College of Sports Medicine: Training load and monitoring resources.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.