Calories burned by heart rate calculator

Updated 26 October 2026

What this does

Enter your sex, age, weight, average heart rate and how long you exercised. You get an estimate of active energy in kilocalories, for the session and per hour.

Two fields are optional. A resting heart rate raises the lowest heart rate that counts. A maximum sets the highest, and left empty it comes from your age. Everything runs in your browser. Nothing you type is sent, stored or logged.

The calculator

The Keytel equation for calories from heart rate

This page uses the Keytel equation, from a 2005 paper by Keytel and colleagues in the Journal of Sports Sciences, in the form without VO2max. It gives gross energy in kilojoules per minute:

• Men: minus 55.0969 plus 0.6309 times heart rate, plus 0.1988 times weight in kg, plus 0.2017 times age.
• Women: minus 20.4022 plus 0.4472 times heart rate, minus 0.1263 times weight in kg, plus 0.0740 times age.

Divide by 4.184 for kilocalories. The headline figure here is active energy: gross minus resting, where resting is 3.5 times your weight in kg divided by 200 per minute, one MET. Active energy is what Apple Health calls active energy, and what Beatcast shows.

Source: Keytel LR, Goedecke JH, Noakes TD et al. Prediction of energy expenditure from heart rate monitoring during submaximal exercise. Journal of Sports Sciences, 2005, 23(3): 289-297. DOI 10.1080/02640410470001730089.

A worked example

Take a 40-year-old man of 80 kg at an average of 140 bpm for 30 minutes.

1. Gross energy per minute: minus 55.0969, plus 0.6309 times 140 (88.33), plus 0.1988 times 80 (15.90), plus 0.2017 times 40 (8.07). That makes 57.20 kJ.
2. In kilocalories: 57.20 divided by 4.184 is 13.67 kcal a minute.
3. Resting: 3.5 times 80, divided by 200, is 1.40 kcal a minute.
4. Active: 13.67 minus 1.40 is 12.27 kcal a minute.
5. Over 30 minutes, that comes to about 368 active kilocalories.

For a 40-year-old woman of 65 kg at the same heart rate: minus 20.4022, plus 0.4472 times 140 (62.61), minus 0.1263 times 65 (8.21), plus 0.0740 times 40 (2.96). That is 36.96 kJ, or 8.83 kcal a minute. Resting is 1.14, which leaves 7.70 active kcal a minute and about 231 over half an hour.

Active or gross

Most calculators show the gross figure, which includes what your body burns at rest anyway. For the man above, gross over 30 minutes is about 410 kilocalories and active is 368. The 42 between them is what he would have used sitting still. The calculator shows the gross total too, smaller, as the equation's own figure.

When this equation does not apply

It was fitted on steady effort, in 115 fit adults aged 18 to 45, with nothing below 57 percent of maximum. Rest, strength sets, intervals, heat and illness are outside it.

There is also a floor. If your heart rate is under 90 beats per minute, the calculator says the result is outside the range the equation covers and shows no number. Enter a resting rate and the floor can rise, to your resting rate plus a tenth of the gap to your maximum. Above your maximum, it uses the maximum.

The equation is a straight line in heart rate, so an average heart rate gives the same total as a second-by-second sum when nothing is clipped. The app sums per second and applies the floor to each reading.

How accurate is a heart rate calorie estimate

It is an estimate from heart rate, not a measurement. On a steady endurance effort between about 90 beats per minute and 90 percent of your maximum, studies comparing heart rate estimates with measured energy use find them within about a fifth for a group of people. One person's figure can be off by more.

On the paper's own validation sample of 17 people, the no-VO2max equation ran high on average, by about 1.5 kilocalories a minute. Do not use it for diet or medical decisions.

These are training estimates. If you take medication that changes your heart rate or have a heart condition, ask your clinician before using age-based numbers. Beatcast is not a medical device.

Calories burned at 110 to 160 bpm (30 minutes)

Active kilocalories over 30 minutes at a steady heart rate, for a 40-year-old, from the same function.

Men

Women

The women's figures fall as weight rises. That is what the published equation does, because its weight coefficient is negative. It is one more reason to read the result as a rough estimate.

Calories burned per hour

Active kilocalories in 60 minutes at a steady heart rate, for a 40-year-old, from the same function. Few sessions hold one heart rate for an hour, so treat these as a scale.

Calories from heart rate on an iPhone

The optional calorie estimate in Beatcast uses this equation per second during a session, with a Bluetooth heart rate sensor. It counts only active energy, and it is off until you switch it on. Weight and sex are used for nothing else. Switched on, it appears next to heart rate and elapsed time, and goes with the session to your history, the CSV and TCX exports and Apple Health if you save sessions there.

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Questions

Good to know

Beatcast is not a medical device. It is built for training and general wellbeing, and it cannot detect, diagnose, treat or monitor any condition. If something about your heart worries you, talk to a doctor rather than to an app.

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