The Calories Burned Calculator estimates energy expenditure for over 120 activities using standardised MET values from the Ainsworth 2011 Compendium.
Why Every Calorie Burn Estimate Is an Approximation
Before examining the formula, it is worth understanding what a calorie burn figure actually represents. Every number this tool produces is a population-level estimate — derived from averages measured across groups of research participants in laboratory settings. Your actual energy expenditure for the same activity, at the same duration and body weight, could differ by 15–20% in either direction. That is not a flaw in the formula; it reflects genuine biological variation in how individual bodies use energy.
Several factors drive that variation. Mechanical efficiency matters: a trained runner uses less energy per kilometre than a novice because their stride is more economical. Body composition plays a role too — two people weighing 75 kg will burn different amounts if one carries 15% body fat and the other carries 30%, because muscle tissue is more metabolically active than adipose tissue. Genetics, environmental temperature, caffeine intake, and even altitude all nudge the real number away from the estimate. Treat MET-based calculations as a useful starting point for comparison and planning, not as a precise measurement of your personal expenditure.
How MET-Based Calorie Calculation Works
The MET system assigns a standardised energy cost to each activity relative to quiet sitting. One MET equals approximately 1 kcal per kilogram of body weight per hour — the energy cost of rest. An activity rated at 7.0 METs therefore costs roughly seven times the energy of sitting still. You can browse the full MET value reference table for all activities to see how different exercise types compare.
The core formula is straightforward:
Calories burned = MET value × body weight (kg) × duration (hours)
This equation works because MET values already encode the relative energy cost of the activity. Multiplying by body weight scales the estimate to the individual (heavier bodies require more energy to perform the same movement), and multiplying by duration accounts for how long the activity is sustained. The result is an estimate in kilocalories.
For activities with variable intensity — such as circuit training where effort spikes and dips — the assigned MET represents an average across the typical pattern. This is one reason estimates are less precise for interval-style exercise than for steady-state work like jogging or cycling at a constant pace.
Why Body Weight Changes Everything
The linear relationship between body weight and calorie burn is one of the most practical insights from the MET system. A 90 kg person jogging at MET 7.0 burns roughly 630 kcal per hour, while a 60 kg person doing the same jog burns approximately 420 kcal per hour — a 50% difference for identical effort and duration. This has direct implications for anyone using exercise as part of a total daily energy expenditure breakdown.
This scaling also explains why calorie burn from walking-specific calorie and step tracking can be surprisingly meaningful for heavier individuals. A brisk walk at MET 5.0 for a 100 kg person burns over 500 kcal per hour — comparable to what a lighter person would expend during moderate cycling. The MET system captures this proportionality automatically.
Myth-Bust: "The Fat Burning Zone"
The "fat burning zone" is one of the most persistent misconceptions in exercise physiology. The claim is that exercising at lower intensities (typically 55–65% of maximum heart rate) burns more fat than higher-intensity work, and that this makes low-intensity exercise superior for fat loss. The first half of that claim is technically correct; the conclusion drawn from it is not.
At lower intensities, a higher percentage of total energy does come from fat oxidation — roughly 60% of calories from fat at moderate effort versus 35–40% at vigorous effort. But the absolute numbers tell a different story. Consider two scenarios for the same person over 30 minutes:
| Intensity | Total kcal | % from fat | Fat kcal burned |
|---|---|---|---|
| Moderate walk (MET 3.5) | 147 | 60% | 88 |
| Vigorous run (MET 9.8) | 412 | 35% | 144 |
The vigorous session burns 64% more fat calories despite drawing a lower percentage from fat. Higher intensity produces greater total energy expenditure, and a larger slice of a much bigger pie still yields more. For running pace and split time calculations at various intensities, faster paces consistently produce higher per-minute calorie costs.
None of this means low-intensity exercise is without value. Walking and light cycling are sustainable, joint-friendly, and can be maintained for longer durations — all of which contribute meaningfully to total weekly energy expenditure. If you track walking by steps rather than time, a step count to distance conversion translates your daily count into kilometres for a more intuitive sense of volume. The point is simply that "staying in the fat burning zone" is not a superior fat loss strategy compared to exercising at whatever intensity you can sustain consistently.
EPOC: The Afterburn Effect in Context
EPOC refers to the elevated metabolic rate that persists after exercise ends — sometimes called the "afterburn effect." High-intensity and resistance training produce greater EPOC than steady-state cardio, with estimates ranging from 50 to 200 additional kcal over several hours depending on intensity and duration. While EPOC is real and measurable, its practical contribution to fat loss is modest compared to the calories burned during the session itself. It is a genuine physiological benefit of vigorous training, but not the game-changing calorie bonus that some sources suggest. Adequate hydration during and after exercise supports the recovery processes that underpin EPOC.
Practical Uses for Calorie Burn Data
The most valuable application of MET-based estimates is comparison rather than precision. Knowing that swimming laps at MET 5.8 burns roughly 70% of what running at MET 8.3 burns — for the same person and duration — helps with activity selection and time allocation. If your goal is maximum calorie expenditure per unit of time, the comparison table in this calculator highlights which activities deliver the most energy cost.
For weight management, exercise calorie estimates feed into the larger energy balance equation. Your total daily energy expenditure combines basal metabolic rate, the thermic effect of food, non-exercise activity thermogenesis, and exercise activity. This calculator addresses only the exercise component. Pairing it with a deficit or surplus plan from the calorie deficit and surplus calculator provides a more complete picture of your energy balance.
Key Terms
MET (Metabolic Equivalent of Task)
A standardised unit expressing the energy cost of an activity relative to rest. One MET equals approximately 3.5 mL of oxygen consumed per kilogram of body weight per minute, or roughly 1 kcal/kg/hour. The Ainsworth 2011 Compendium catalogues MET values for over 800 specific activities based on laboratory measurement and field validation. Values range from 0.9 (sleeping) to over 18 (running at 10.9 mph).
EPOC (Excess Post-Exercise Oxygen Consumption)
The measurable increase in oxygen consumption — and therefore calorie expenditure — that occurs after exercise as the body restores homeostasis. EPOC covers processes such as glycogen resynthesis, lactate clearance, elevated heart rate, and tissue repair. The magnitude and duration of EPOC scale with exercise intensity, which is why high-intensity intervals and heavy resistance training produce greater afterburn effects than moderate steady-state cardio.
NEAT (Non-Exercise Activity Thermogenesis)
All energy expended through physical activity that is not deliberate exercise. NEAT includes fidgeting, standing, walking between rooms, household chores, and occupational movement. For most people, NEAT accounts for a larger share of daily energy expenditure than formal exercise sessions. Individuals vary enormously in NEAT — some people unconsciously increase movement when overfed and decrease it when underfed, which partly explains differences in weight gain susceptibility across individuals with similar diets.