TDEE & Calorie Calculator
Quick answer
Total daily energy expenditure is your basal metabolic rate multiplied by an activity factor. Mifflin-St Jeor gives BMR as 10 × kg + 6.25 × cm − 5 × age, plus 5 for men or minus 161 for women.
Daily calorie needs
Mifflin-St Jeor BMR × activity factor.
Maintenance calories
2,322
kcal per day at this activity level
BMR (at rest)
1,689 kcal
To lose ~0.5 kg/week
1,822 kcal
An estimate, not a prescription. Individual metabolic rate varies by around ±200 kcal/day for identical inputs. Recalculate every 4–6 kg of change.
Your body burns calories in three places: keeping you alive at rest, digesting food, and moving. Basal metabolic rate covers the first and is by far the largest share — typically 60 to 70 per cent of the total for someone who is not an athlete.
The Mifflin-St Jeor equation has been the standard estimate since 1990 because it outperformed the older Harris-Benedict formula in validation studies. It is still an estimate: individual metabolic rate varies by roughly 200 calories a day either side of the prediction for the same height, weight, age and sex.
Choosing the right activity factor
The multipliers are 1.2 for sedentary, 1.375 for light exercise one to three days a week, 1.55 for moderate exercise three to five days, 1.725 for hard exercise six to seven days, and 1.9 for physical work or twice-daily training.
Almost everyone overestimates here. A desk job with three gym sessions a week is light to moderate, not hard. If your weight is not moving on the number the calculator gives, the activity factor is the first thing to revise down.
Deficits that hold, and deficits that do not
A deficit of roughly 500 calories a day corresponds to about half a kilogram of fat a week. Larger deficits work at first and then stop working, because adherence collapses and the body reduces spontaneous movement.
Weight also does not fall in a straight line. Glycogen binds water at roughly three grams of water per gram of glycogen, so the first week of a deficit shows a large drop that is mostly water, and a single high-carbohydrate day can put two kilograms back on the scale without adding any fat.
Why the number drifts as you lose weight
BMR scales with body mass. Lose ten kilograms and the equation gives a lower maintenance figure, so a deficit that worked at the start becomes maintenance later. Recalculate every four to six kilograms.
Protein intake and resistance training matter here for a specific reason: they determine how much of the weight lost is fat rather than lean tissue. Lean mass is metabolically active, so preserving it keeps the maintenance figure higher.
Frequently asked questions
- Is Mifflin-St Jeor better than Harris-Benedict?
- Yes for most people. Mifflin-St Jeor was validated against indirect calorimetry in 1990 and predicts resting energy expenditure more accurately in non-obese and obese adults alike.
- How many calories should I eat to lose weight?
- Roughly 500 below your TDEE for about half a kilogram a week. Going much lower rarely speeds things up in practice because adherence falls and non-exercise movement drops.
- Does this account for body composition?
- No. Mifflin-St Jeor uses height, weight, age and sex only. If you know your body fat percentage, the Katch-McArdle formula based on lean mass will be more accurate, particularly for very lean or very heavy people.
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Updated 2026-09-20 · all calculators. Results are estimates for guidance, not professional advice.