Calories Burned Calculator
Enter your body weight, activity, and duration for a science-based calorie estimate using MET values from the Compendium of Physical Activities. Switch to heart rate mode for a personalised result based on your age, sex, and average heart rate during exercise.
Formula
Worked example
MET mode: Running at 6 mph (MET 9.8) for 30 min at 70 kg: 9.8 x 70 x 0.5 = 343 kcal. Heart rate mode (male, 30 yr, 70 kg, 145 bpm): 30 x (0.6309x145 + 0.1988x70 + 0.2017x30 - 55.0969) / 4.184 = approx 305 kcal.
How the MET formula works
The standard formula is: kcal burned = MET x weight in kg x duration in hours. MET (Metabolic Equivalent of Task) measures how much energy an activity requires relative to sitting still at rest (MET 1.0). Walking at a moderate pace has a MET of about 3.5, running at 6 mph carries roughly 9.8, and sleeping is close to 1.0. The formula is based on the fact that oxygen consumption, and therefore caloric cost, scales linearly with both body mass and time at a given effort level. Values come from the Compendium of Physical Activities, a peer-reviewed database of over 800 activities maintained by researchers at Arizona State University.
Heart rate mode: a more personalised estimate
When you supply your average heart rate during exercise, the calculator switches to the Keytel et al. (2005) formula, which also accounts for your age and sex. Because heart rate correlates with actual oxygen consumption, this approach can be more accurate than looking up an activity from a generic table, particularly for workouts that vary in intensity. The formula differs between males and females because men and women have different relationships between heart rate and energy expenditure at the same absolute workload. If you have a fitness tracker or chest strap, enter your session-average bpm for a better result.
What the burn rate and fat loss outputs mean
The burn rate (kcal/h) tells you how intense the activity is relative to time, independent of how long you actually exercised. This is useful for comparing activities of different durations. The fat loss estimate is a rough guide: one gram of body fat stores about 7.7 kcal, so dividing your total burn by 7.7 gives the grams of fat you could lose if every calorie came from fat oxidation. In practice, the body also burns carbohydrates and protein, and exercise increases appetite, so actual fat loss from a single session is smaller than this number. Think of it as an upper bound for context, not a target.
Comparing two activities side by side
The comparison mode lets you run a second activity with its own duration and see both totals together, along with a chart that plots how each accumulates calories over time. This is helpful for deciding between workout options or understanding the trade-off between intensity and duration. For example, 30 minutes of running at 6 mph burns around 343 kcal for a 70 kg person, while 60 minutes of walking at 3 mph burns roughly 245 kcal at the same weight, a good illustration of how intensity and time interact.
Accuracy and limitations of calorie estimates
MET-based calculations are derived from population averages and assume steady-state effort throughout the session. Individual results can vary by 10 to 20 percent depending on fitness level, muscle efficiency, terrain, temperature, and metabolic rate. Highly trained athletes tend to burn slightly fewer calories per unit of effort than beginners because their movement mechanics are more efficient. The formula also does not capture the post-exercise oxygen consumption (EPOC) effect, which can add a meaningful extra burn after intense interval or resistance training sessions. Heart rate mode reduces some of this variability but still carries measurement uncertainty from heart rate device accuracy and individual physiology.
MET values for common activities
| Activity | MET | Intensity |
|---|---|---|
| Sleeping | 0.95 | Rest |
| Sitting / desk work | 1.5 | Sedentary |
| Walking: slow (2 mph) | 2.5 | Light |
| Yoga (general) | 2.5 | Light |
| Walking: moderate (3 mph) | 3.5 | Light |
| Weight training (general) | 3.5 | Light |
| Cycling: leisurely | 4 | Moderate |
| Golf (walking) | 4.5 | Moderate |
| Hiking (general) | 6 | Moderate |
| Swimming: leisure | 6 | Moderate |
| Rowing machine (moderate) | 7 | Moderate |
| Cycling: moderate (12-14 mph) | 8 | Vigorous |
| Running: 5 mph | 8.3 | Vigorous |
| HIIT | 8 | Vigorous |
| Running: 6 mph | 9.8 | Vigorous |
| Martial arts | 10 | Vigorous |
| Running: 7 mph | 11 | Very vigorous |
| Cycling: very fast (> 16 mph) | 12 | Very vigorous |
| Running: 10 mph | 14.5 | Very vigorous |
Sourced from the 2011 Compendium of Physical Activities. Higher MET = more calories per minute at the same body weight.
Frequently asked questions
How accurate is a MET-based calorie burn estimate?
MET-based calculations are accurate to within roughly 10 to 20 percent for most steady-state aerobic activities when body weight and duration are entered correctly. Accuracy drops for highly variable activities like team sports or HIIT, where effort fluctuates. Individual metabolic variation, fitness level, and environmental conditions all contribute to the gap between the estimate and your true burn. Heart rate mode narrows this gap by personalising the formula to your actual physiological response.
Why does body weight affect calories burned so much?
Body weight is directly proportional in the MET formula because moving a heavier body requires more mechanical work against gravity. Every extra kilogram of body weight increases caloric expenditure at the same activity intensity. This effect is largest in weight-bearing activities like walking and running, and smaller (but still present) in non-weight-bearing activities like cycling or swimming where buoyancy or the seat supports some of the mass.
What is the difference between MET mode and heart rate mode?
MET mode assigns a fixed energy cost to an activity type and multiplies by your weight and time. It requires no special equipment and gives a reasonable population-average estimate. Heart rate mode uses the Keytel formula (published in the Journal of Sports Sciences, 2005) with your measured heart rate, age, sex, and weight to estimate oxygen consumption more directly. Heart rate mode is generally more accurate for individuals because it reflects your actual cardiovascular response, but it requires a heart rate measurement from a fitness tracker or chest strap.
How is the fat loss estimate calculated?
One gram of body fat contains approximately 9 kcal of energy, but the metabolic efficiency of fat oxidation means only about 7.7 kcal of usable energy is released per gram burned. Dividing your total calorie burn by 7.7 gives the theoretical maximum grams of fat that could be lost from one session. In reality, your body also uses carbohydrates and protein for fuel, so actual fat loss per workout is lower. Over time, consistent calorie deficits are what drive fat loss, not single sessions.
Can I use a custom MET value?
Yes. Toggle on the custom MET option in MET mode to enter your own value. This is useful if your activity is not in the dropdown, if you are working at a non-standard intensity, or if you have a measured MET from a metabolic test. MET values range from about 0.9 for sleeping to 23 for elite sprinting. The 2011 Compendium of Physical Activities, freely available from Arizona State University, lists over 800 activities with assigned MET codes.
How many calories do I need to burn to lose 1 kg of fat?
One kilogram of body fat stores roughly 7,700 kcal (one pound stores about 3,500 kcal). A daily deficit of 500 kcal from a combination of exercise and reduced food intake would, in theory, produce about 0.5 kg of fat loss per week. In practice, metabolic adaptation, water retention, and changes in muscle mass mean actual results vary. Exercise alone rarely produces large deficits; combining it with dietary changes is more effective for sustained fat loss.