Calories Burned by Heart Rate Calculator (Keytel formula)

Understanding the calories burned by heart rate calculator — concept and principle

This calculator estimates the energy you used during exercise from your average heart rate, sex, age, weight and exercise time, using the Keytel (2005) equations. It shows total kilocalories, kcal per minute and per hour, and kilojoules. Runners, cyclists and gym users with heart-rate monitors use it.

Heart rate → energy used — with the default inputs: 583 kcal.

How it is calculated

Men: kJ/min = −55.0969 + 0.6309 × HR + 0.1988 × weight (kg) + 0.2017 × age
Women: kJ/min = −20.4022 + 0.4472 × HR − 0.1263 × weight (kg) + 0.074 × age
kcal/min = kJ/min ÷ 4.184
Total = kcal/min × minutes

The principle

During steady exercise, heart rate rises roughly in line with oxygen uptake, and oxygen uptake reflects energy use. Keytel and colleagues measured oxygen uptake and heart rate in 115 adults and fitted equations that also account for sex, weight and age. The version without VO₂max assumes an average fitness level. It works best for moderate to hard steady exercise.

Worked example

Defaults: man, 35 years, 70 kg, average heart rate 140 bpm, 45 minutes.

kJ/min = −55.0969 + 88.326 + 13.916 + 7.060 = 54.20.
kcal/min = 54.20 ÷ 4.184 = 13.0.
Total = 12.955 × 45 = 583 kcal; per hour 777 kcal.
Energy = 54.20 × 45 = 2,439 kJ.

Each point is the calculator re-run with only “Exercise time (minutes)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Exercise time (minutes)	Calories burned (kcal)
11.2	146
22.5	291
33.8	437
45	583
56.2	729
67.5	874
90	1,166

How to read the result

Treat the figure as a rough estimate; individual results can be well off. It is less accurate at rest, in very short intervals, and with medicines that change heart rate, such as beta-blockers. Fitter people tend to have lower heart rates for the same work, so the equation may underestimate their energy use.

Common mistakes

Using peak heart rate instead of the average.
Applying it to interval sessions with rapid swings.
Adding the result fully to your daily calorie allowance; part of it would have been burned at rest anyway.
Comparing values from devices that use different formulas.

Keep in mind: Not medical advice. If you have heart disease or take medicines affecting heart rate, ask your doctor about safe exercise.

Frequently asked questions

How accurate is calorie estimation from heart rate?

Reasonable for groups in steady exercise, but individual errors can be large.

Why does the formula differ for men and women?

The study found different relationships between heart rate and energy use by sex.

How many kcal is 1 kJ?

1 kcal = 4.184 kJ, so 1 kJ ≈ 0.239 kcal.

Sources: Keytel LR, Goedecke JH, Noakes TD, et al., "Prediction of energy expenditure from heart rate monitoring during submaximal exercise", J Sports Sci 2005;23(3):289–297

Checked 9 Nov 2026. Keytel LR, Goedecke JH, Noakes TD, et al., “Prediction of energy expenditure from heart rate monitoring during submaximal exercise”, J Sports Sci 2005;23(3):289–297 (equations without VO₂max); 1 kcal = 4.184 kJ (thermochemical calorie).

Your numbers