Health & Fitness · Guide
How to Calculate Calories Burned Based on Heart Rate
Your heart rate shows how hard you are working. With your age and weight, it gives a decent calorie estimate.
Want the answer for your own numbers? Use the free Calorie Calculator — it does every step below for you.
Why heart rate works
During steady exercise, heart rate rises almost in step with the oxygen your muscles use — and oxygen use tracks calories burned. That is why many fitness watches use heart rate. The most widely used formula comes from a 2005 study by Keytel and colleagues.
The heart rate calorie formula (Keytel)
Men: kcal/min = (−55.0969 + 0.6309×HR + 0.1988×W + 0.2017×A) ÷ 4.184
Women: kcal/min = (−20.4022 + 0.4472×HR − 0.1263×W + 0.074×A) ÷ 4.184
HR is your average heart rate in beats per minute, W is weight in kilograms, and A is age in years. Multiply the result by your minutes of exercise.
Worked example
A 35-year-old man, 80 kg, average heart rate 140, for 30 minutes
−55.0969 + (0.6309 × 140) + (0.1988 × 80) + (0.2017 × 35)
= −55.10 + 88.33 + 15.90 + 7.06 = 56.19. Divide by 4.184 = 13.4 kcal a minute.
13.4 × 30 = about 403 calories
Chart: 30 minutes of exercise
Using the formula for a 35-year-old man of 80 kg and a 35-year-old woman of 65 kg:
| Average heart rate | Man, 80 kg | Woman, 65 kg |
|---|---|---|
| 100 bpm | 222 kcal | 134 kcal |
| 120 bpm | 312 kcal | 198 kcal |
| 140 bpm | 403 kcal | 262 kcal |
| 160 bpm | 493 kcal | 326 kcal |
When the formula works best — and when it does not
- Best for: steady cardio such as running, cycling, rowing or brisk walking, at heart rates roughly between 90 and 150 bpm.
- Less reliable for: weight lifting and interval training, where heart rate jumps around.
- Affected by: heat, caffeine, stress, dehydration and medicines such as beta-blockers, which change heart rate without changing calorie burn.
- Fitness level: fitter people burn calories at a lower heart rate, so the formula may undercount for them. A VO2max-based version exists if you know yours.
A second worked example
A 40-year-old woman, 65 kg, average heart rate 150, for 45 minutes
−20.4022 + (0.4472 × 150) − (0.1263 × 65) + (0.074 × 40)
= −20.40 + 67.08 − 8.21 + 2.96 = 41.43. Divide by 4.184 = 9.9 kcal a minute.
9.9 × 45 = about 446 calories
Find your heart rate zones
The formula needs your average heart rate, and zones help you plan it. First estimate your maximum heart rate. The classic rule is 220 − age. A newer formula, 208 − 0.7 × age, is often a little more accurate for older adults. Then take percentages of it:
| Age | Max HR (220 − age) | Zone 2 (60–70%) | Zone 3 (70–80%) | Zone 4 (80–90%) |
|---|---|---|---|---|
| 25 | 195 | 117–136 | 136–156 | 156–176 |
| 35 | 185 | 111–130 | 130–148 | 148–166 |
| 45 | 175 | 105–122 | 122–140 | 140–158 |
| 55 | 165 | 99–115 | 115–132 | 132–148 |
These are population estimates. Your true maximum can differ by 10 beats or more, so treat the zones as a guide.
Check it another way: the MET method
You can cross-check with a MET value. Running at 6 mph is about 9.8 METs. For the same 80 kg man running for 30 minutes: 9.8 × 3.5 × 80 ÷ 200 × 30 = about 412 calories. The heart rate method gave 403. When two independent methods agree that closely, you can trust the ballpark.
Putting it in context
Exercise is usually a smaller share of daily calories than people expect. Your body burns most of its energy at rest — your BMR. See your resting burn in the BMR calculator, and your full daily needs in the calorie calculator.
Frequently asked questions
Use the Keytel formula with your average heart rate, weight and age, then multiply by minutes of exercise. A 35-year-old, 80 kg man averaging 140 bpm burns about 13.4 calories a minute, or roughly 400 in 30 minutes.
It is reasonable for steady cardio. It is less accurate for weights or intervals, and for anyone on medicines that change heart rate.
It depends on your weight, age and sex. Using the Keytel formula, a 35-year-old man weighing 80 kg burns about 10.4 calories a minute at 120 bpm, and a 35-year-old woman weighing 65 kg about 6.6 — roughly 312 and 198 calories in 30 minutes.
Watches combine heart rate with motion data and their own private formulas, and wrist sensors can misread heart rate during some exercise. Studies find calorie estimates from wearables can be off by 20% or more. Use one method consistently and watch the trend rather than the exact figure.
Sources and further reading
- Keytel et al., Journal of Sports Sciences (2005) — prediction of energy expenditure from heart rate
- Tanaka H et al. (2001), Journal of the American College of Cardiology — the 208 − 0.7 × age maximum heart rate formula
- Compendium of Physical Activities — the standard reference for MET values of walking and other activities