Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Calories Burned by Heart Rate Is Calculated
Calories burned by heart rate is an estimate of the energy your body used during exercise, worked out from how fast your heart was beating. During steady exercise, heart rate and oxygen use rise together, and oxygen use tracks energy use, so a research equation can turn your average heart rate into calories.
What Calories Burned by Heart Rate Measures
The result is the total energy you used during the workout, including what your body would have burned at rest in that time. It is based on how hard your heart worked, not on the name of the activity, so it can reflect a hilly route or a hard pace. It does not measure fat burned.
The Formula
Men: kJ per minute = -55.0969 + 0.6309 x HR + 0.1988 x weight + 0.2017 x age
Women: kJ per minute = -20.4022 + 0.4472 x HR - 0.1263 x weight + 0.074 x age
Men, with VO2 max: kJ per minute = -95.7735 + 0.634 x HR + 0.404 x VO2 max + 0.394 x weight + 0.271 x age
Women, with VO2 max: kJ per minute = -59.3954 + 0.450 x HR + 0.380 x VO2 max + 0.103 x weight + 0.274 x age
Calories per minute = kJ per minute ÷ 4.184
HR is your average heart rate in beats per minute, weight is in kg, age is in years and VO2 max is in ml/kg/min. The equations come from a 2005 study by Keytel and colleagues, who tested 115 regularly exercising adults on a treadmill or exercise bike¹.
How This Calculator Computes Your Result
Enter your sex, age, weight (kg or lb), your average heart rate for the workout and how long it lasted. If you know your VO2 max, add it and the calculator switches to the VO2 max equation. Pounds are converted to kg, the equation gives kJ per minute, and dividing by 4.184 turns that into calories (kcal).
You see total calories, calories per minute and per hour, and the total in kJ. The calculator also compares your heart rate with your estimated max heart rate (208 - 0.7 x age)² and tells you if it falls inside the range the equations were built from. If the equation gives less than a resting burn, about 1 kcal per kg of body weight per hour³, no number is shown.
What Your Result Means
The study's three exercise stages averaged 57%, 77% and 90% of maximum heart rate¹. Your result is most useful when your heart rate sits in that band.
Your average heart rate | What the calculator shows | How much to rely on it |
Under 90 bpm, or under 55% of your estimated max | Below the tested range | A rough figure at best |
55% to 90% of your estimated max | Within the tested range | The best this method can give |
Above 90% of your estimated max | Above the tested range | A rough figure at best |
As a quick reference, here is what the equations give for a 30-minute workout at age 35 without VO2 max (our calculation)¹:
Average heart rate | Man, 80 kg | Woman, 65 kg |
110 bpm | 267 kcal | 166 kcal |
120 bpm | 312 kcal | 198 kcal |
130 bpm | 358 kcal | 230 kcal |
140 bpm | 403 kcal | 262 kcal |
150 bpm | 448 kcal | 294 kcal |
160 bpm | 493 kcal | 326 kcal |
In the VO2 max equation, a higher VO2 max raises the estimate at the same heart rate. For the 80 kg man at 140 bpm, a VO2 max of 35 gives 345 kcal and a VO2 max of 55 gives 403 kcal (our calculation)¹.
Why Heart Rate Fails at Rest and Near Your Max
At low heart rates, heart rate is a weak guide to energy use. Researchers who track calories with heart rate monitors set a cut-off called the FLEX heart rate, which averaged 86 bpm in men and 96 bpm in women in one study, and use measured resting values below it⁴. You can see the problem in the equations. A 30-year-old woman weighing 60 kg at 60 bpm gets 0.26 kcal per minute, about a quarter of her resting burn (our calculation)¹ ³.
Near your max, heart rate cannot climb much further, so extra effort in a sprint does not show up as a higher heart rate. The study did not test efforts above about 90% of max heart rate¹.
Long sessions add a third problem. In one study of 55 minutes of steady cycling, heart rate kept rising while oxygen use did not change⁵. This is called cardiovascular drift, and it makes the later part of a long or hot workout read higher than the work you did.
How Accurate Heart Rate Calorie Estimates Are
In the study, the equation without VO2 max explained 73% of the differences in energy use, and adding VO2 max raised that to 83%¹. The study only included regularly exercising adults aged 18 to 45, doing steady treadmill or bike work¹. Weights, intervals and swimming were not tested.
Fitness watches face the same limits. In a test of seven wrist devices on 60 people, six measured heart rate with under 5% median error during cycling, but none estimated energy use with less than 20% error⁶. A heart rate number and an activity number from the Calories Burned Calculator will often differ, so pick one method and stick with it.
Calories Burned in 30 Minutes by Heart Rate
What the equations give for a 30-minute workout at age 35, without VO2 max.
- Man, 80 kg
- Woman, 65 kg
Show data table
| Average heart rate (bpm) | Man, 80 kg (kcal) | Woman, 65 kg (kcal) |
|---|---|---|
| 110 | 267 | 166 |
| 120 | 312 | 198 |
| 130 | 358 | 230 |
| 140 | 403 | 262 |
| 150 | 448 | 294 |
| 160 | 493 | 326 |
A Note on Accuracy
This is an estimate from a group equation, not a measurement of your own body. It works best for steady cardio at 55% to 90% of your max heart rate in adults aged 18 to 45¹. Heat, long sessions, a loose wrist sensor and medicines that slow the heart can all throw it off.
Frequently Asked Questions
How many calories do you burn at a heart rate of 140?
For 30 minutes at 140 bpm, the Keytel equations give about 400 kcal for an 80 kg man and about 260 kcal for a 65 kg woman, both aged 35 (our calculation)¹. Your own number depends on your age, weight, sex and fitness.
What is a good heart rate to burn calories?
In this formula, a higher heart rate always means more calories per minute, but a pace you can hold longer may burn more in total. The estimate is most reliable between about 55% and 90% of your max heart rate, the range the equations were built from¹.
Is calculating calories by heart rate accurate?
It is a reasonable estimate for steady cardio, but not exact. In the original study the equation without VO2 max explained about 73% of the differences in energy use, and adding VO2 max raised that to 83%¹.
Why does my watch show different calories than this calculator?
Each watch brand uses its own formula, often mixing heart rate with movement and your profile data. In one test of seven wrist devices, none estimated calories with less than 20% error⁶.
Sources
Prediction of Energy Expenditure From Heart Rate Monitoring During Submaximal Exercise, Keytel et al., 2005
Age-Predicted Maximal Heart Rate Revisited, Tanaka et al., 2001
Compendium of Physical Activities, Compendium of Physical Activities
The Use of Heart Rate Monitoring in the Estimation of Energy Expenditure, Ceesay et al., 1989
The Role of Active Muscle Mass on Exercise-Induced Cardiovascular Drift, Kounalakis et al., 2008
Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure, Shcherbina et al., 2017