What is a calories burned estimate?
A calories burned estimate is a population-level calculation that approximates how much energy your body uses during a specific physical activity. It combines a standardized activity intensity rating, known as the Metabolic Equivalent of Task (MET), with your body weight and the duration of the activity. The result is expressed in kilocalories (kcal), the same unit you see on food labels.
This estimate is derived from decades of research on indirect calorimetry, where scientists measured oxygen consumption during exercise across large groups of people. It is not a precise measurement of your personal energy expenditure. It is a population-level estimate and is not medical advice or treatment. It should not be used to prescribe a diet, diagnose a condition, or replace guidance from a registered dietitian, certified exercise physiologist, or other qualified healthcare professional.
The formula behind the calculation
The standard formula used by exercise physiology researchers is:
kcal = MET × 3.5 × body weight in kilograms ÷ 200 × duration in minutes
Each component serves a specific purpose. The MET value captures how many times resting metabolic rate the activity demands. The constant 3.5 represents the assumed resting oxygen consumption in milliliters of oxygen per kilogram of body weight per minute (mL O₂/kg/min). Dividing by 200 converts oxygen consumption into kilocalories, accounting for the caloric equivalent of oxygen and the transition from milliliters to liters. Multiplying by minutes scales the estimate to the total duration of the activity.
Understanding MET values
A MET, or Metabolic Equivalent of Task, is a ratio that compares the energy cost of an activity to the energy cost of sitting quietly. Sitting quietly is defined as 1 MET, which corresponds to roughly 1 kilocalorie per kilogram of body weight per hour for an average adult.
Walking at a moderate pace of around 5 km/h (3 mph) typically registers at about 3.5 METs. Jogging at 8 km/h (5 mph) may fall near 7 to 8 METs. Running at faster speeds or performing high-intensity interval training can push values above 10 METs. Housework, gardening, and occupational tasks each have their own assigned MET values in the Adult Compendium of Physical Activities.
The selection of the correct MET value is the single largest source of variability in the estimate. Two people performing what looks like the same activity may be working at different intensities. The Compendium provides a range of values for many activities to reflect this, but the calculator must pick a single representative number. The estimate is only as accurate as the match between the chosen MET value and the actual intensity the person sustained.
The resting oxygen convention
The formula embeds the assumption that resting oxygen consumption is 3.5 mL O₂/kg/min. This number, sometimes called "1 MET" in physiological terms, is a population average. It was derived from studies of healthy, primarily young to middle-aged adults. Individual resting metabolic rates vary with age, sex, body composition, fitness level, and hormonal status. A person with more lean muscle mass will have a higher resting metabolic rate, while someone with a higher proportion of body fat will have a lower one. The 3.5 constant smooths over all of this variation. The estimate applies this average to everyone, which means it will overestimate expenditure for some people and underestimate it for others.
Worked example
Consider a person who weighs 70 kilograms and jogs for 45 minutes at an intensity of 7 METs.
Plugging the numbers into the formula:
7 × 3.5 × 70 ÷ 200 × 45 = 385.875 kcal
This value is displayed as about 386 kcal.
The calculation multiplies the MET value of 7 by the resting oxygen constant of 3.5, yielding 24.5 mL O₂/kg/min. That figure is multiplied by 70 kilograms of body weight, producing 1,715 mL O₂/min. Dividing by 200 converts this to approximately 8.575 kcal per minute. Over 45 minutes, the total reaches 385.875 kcal, rounded to about 386 kcal for display purposes.
This is a population-level estimate. It tells you what the average 70-kilogram person would expend jogging at 7 METs for 45 minutes. It does not tell you exactly what your body burned.
How to interpret the estimate
The number should be read as a rough guide, not a precise ledger entry. It is most useful for comparing the relative energy demands of different activities. If activity A yields 300 kcal and activity B yields 150 kcal for the same duration, you can reasonably conclude that activity A is about twice as demanding. Small differences of 10 or 20 kcal between activities are not meaningful.
The estimate can help you understand the general magnitude of energy expenditure associated with different forms of movement. It is not a tool for balancing a daily calorie budget down to the last kilocalorie. Food labels, wearable device readings, and metabolic estimates all carry their own margins of error. Adding them together compounds the uncertainty. For this reason, the estimate should not be used to prescribe diet or to adjust food intake with precision.
Accuracy and limitations
Several factors create a gap between the estimated value and what your body actually burns.
Individual physiology. Age, sex, genetics, body composition, and fitness level all influence metabolic rate. A trained athlete and a sedentary person of the same weight will burn different amounts of energy performing the same task.
Intensity drift. A person may start an activity at a steady pace and gradually slow down without realizing it. The MET value assumes a consistent intensity. If intensity drops, the estimate will overstate expenditure.
Environmental conditions. Temperature, humidity, altitude, and wind resistance all affect energy cost. Running into a headwind or in high heat demands more energy than running on a calm, cool day, even at the same speed.
Wearable devices and equipment. Heart rate monitors, fitness trackers, and smartwatches use proprietary algorithms that may produce different numbers than the formula-based estimate. None of these devices measure energy expenditure directly; they all estimate it from proxy signals such as heart rate, movement patterns, and user-entered profile data.
MET value selection. The Compendium assigns MET values based on laboratory studies of groups. The value for "running, 8 km/h" represents an average across study participants. Your personal energy cost at that speed may differ.
Resting metabolic rate variability. As noted, the 3.5 constant is an average. Individual resting metabolic rates can deviate by 10 to 20 percent or more from this figure.
Because of these limitations, the estimate should be treated as a population-level reference point. It is not a diagnosis, not a prescription, and not a substitute for individualized assessment by a qualified professional.
Sources
- Adult Compendium of Physical Activities: https://pacompendium.com/
- Centers for Disease Control and Prevention — Physical Activity for Healthy Weight: https://www.cdc.gov/healthy-weight-growth/physical-activity/index.html
Editorial record
This article was developed by the SoupCalc Editorial Team to provide a clear, evidence-based explanation of how calories burned estimates are calculated and what they mean. It draws on publicly available research and authoritative health-education resources. The content was reviewed for accuracy, clarity, and alignment with current exercise physiology standards. No clinician reviewed this article. This information is an estimate and is not a diagnosis or medical advice or treatment. Author: SoupCalc Editorial Team Last reviewed: August 11, 2026.