Calories Burned Calculator

Your daily energy expenditure is the sum of four things: the energy your body spends at complete rest, the energy it spends digesting what you eat, deliberate exercise, and everything else you do while awake — walking to the car, standing, fidgeting.

Resting metabolism is the largest share of it for almost everyone, usually 60 to 70 per cent. Exercise is the part people count and the smaller part of the total.

Resting metabolism

60 – 70%Breathing, circulation, brain, organ function, cell repair

Everything else you do awake

15 – 30%Walking, standing, chores, fidgeting

Digesting food

~10%Highest for protein, lowest for fat

Deliberate exercise

0 – 15%For most people, the smallest slice

Body size moves it most — a larger body costs more to run, which is why the figure falls as you lose weight and why a target set in January stops working by March.

• Weight and height: more tissue to maintain, more energy spent maintaining it.
• Lean mass: muscle is metabolically busier than fat, though the difference at rest is smaller than most people assume.
• Age: resting rate drifts down through adult life, partly because lean mass does.
• Activity: not just training, but the hours around it — the difference between a desk job and a job on your feet is larger than the difference between three and five gym sessions.

The equation cannot see your body composition. Two people of the same height, weight, age and sex get the same answer, whatever they are made of.

This is a predictive equation, not a measurement. Measuring expenditure properly needs indirect calorimetry or doubly labelled water. Mifflin–St Jeor was chosen here because it is the equation that holds up best against measured values in healthy adults — not because it is exact.

• It is typically within about 10% of measured expenditure, and wider at the extremes of body size.
• The activity multipliers are broad brackets, so honest self-rating matters more than the decimal places.
• It does not account for thyroid disease, some medications, pregnancy or a recent history of heavy dieting, all of which shift resting rate.
• It cannot tell you what you actually ate, which is where most calorie targets go wrong.

The useful way to use it: take the figure, eat at it for two or three weeks, weigh yourself on the same terms each time, and adjust from what the scale did rather than from what the equation said.

First the resting rate, in kcal per day, from the Mifflin–St Jeor equation:

Men

(10 × kg) + (6.25 × cm) − (5 × age) + 5

Women

(10 × kg) + (6.25 × cm) − (5 × age) − 161

Then that figure is multiplied by the activity factor — 1.2 at sedentary through 1.9 at athlete. A 35-year-old man, 178 cm, 84 kg, moderately active: resting rate 1,783, × 1.55 = about 2,763 kcal a day.

Imperial entries are converted to kilograms and centimetres first, so both toggles return the same answer.