Calorie Calculator

Target (kcal/day) = BMR × activity factor + daily deficit

BMR

Basal metabolic rate from sex, age, height and weight (kcal)

activity factor

Multiplier carried by the activity level you pick

daily deficit

7700 kcal per kilogram of body weight, spread over seven days (kcal)

Use it once you have a goal in mind. Both BMR and TDEE are printed, so the arithmetic can be checked by hand: TDEE minus the deficit gives the target. For the resting number on its own, see the BMR calculator; to see what exercise adds to the day, use the calories burned calculator.

1. A 30-year-old man, 175 cm and 70 kg, moderately active, losing 0.5 kg a week

   1. BMR: 10 × 70 + 6.25 × 175 − 5 × 30 + 5 = 1648.75 kcal
   2. Activity factor for moderately active: × 1.55 → 2555.56, rounded to 2556 kcal
   3. Goal of 0.5 kg a week: 7700 × 0.5 ÷ 7 = 550 kcal
   4. Target: 2556 − 550 = 2006 kcal/day
   5. In kilojoules: 2006 × 4.184 = 8393 kJ

   The 550 kcal gap is what a half kilo a week costs per day, and it is the number to hold against what you actually eat.

2. The same man switching to maintenance

   1. BMR is unchanged: 1648.75 kcal
   2. Activity factor unchanged: × 1.55 → 2556 kcal
   3. A maintenance goal asks for no gap, so the deficit is 0
   4. Target: 2556 − 0 = 2556 kcal/day
   5. In kilojoules: 2556 × 4.184 = 10694 kJ

   Maintenance is the anchor. Any target above it adds weight, any target below it removes it — every other row in the chart is this number plus or minus a gap.

3. A 25-year-old woman, 155 cm and 50 kg, sedentary, aiming to lose 0.75 kg a week

   1. BMR: 10 × 50 + 6.25 × 155 − 5 × 25 − 161 = 1182.75 kcal
   2. Activity factor for sedentary: × 1.2 → 1419.3, rounded to 1419 kcal
   3. Goal of 0.75 kg a week: 7700 × 0.75 ÷ 7 = 825 kcal
   4. Target: 1419 − 825 = 594 kcal/day
   5. 594 sits below the 1,200 kcal floor, so the badge reads too low

   Nothing is wrong with the arithmetic — the goal is wrong for this body. A slower rate, or a higher activity level, moves the target back above the floor.

The deficit assumes every kilogram lost is fat, at 7,700 kilocalories. Early loss is part water and lean tissue, so a 0.5 kg weekly target runs ahead of plan at first and then slows — treat the number as a starting point, not a curve. Intakes under about 1,200 kilocalories a day are flagged, because that is the low end of the range guidelines prescribe for losing weight outside medical supervision. The equation predicts an average healthy adult: pregnancy, thyroid disease and some medications all change the picture.

What is a calorie calculator?

A calorie calculator turns your body measurements and activity level into a daily energy target. It estimates basal metabolic rate with the Mifflin-St Jeor equation, scales it by an activity factor to get TDEE, then applies the weight goal you choose. The output is a starting intake, not a fixed rule.

How many calories should I eat to lose weight?

A deficit of 500 to 750 kilocalories a day below your maintenance level usually produces about 0.5 to 0.75 kg a week. That sits inside the 1 to 2 pounds a week that public health guidance calls a safe rate for weight loss. Bigger deficits drop weight faster at first, but a larger share of what leaves is water and muscle.

Why is my calorie target below my BMR?

Because a large deficit subtracted from a small total lands under the resting floor. Very-low-calorie diets do work this way under supervision, but on your own a target under your BMR is a sign to slow the rate down or move more. Anything under 1,200 kilocalories is flagged too, since that is below the range guidelines prescribe without supervision.

Is the 7,700 calorie rule accurate?

It is a good first approximation and a poor long-run prediction. The figure assumes the weight you lose is pure fat, which holds roughly for the first weeks of a diet and less well afterwards as water and lean tissue enter the mix. Real expenditure also falls as you lose weight, so the same deficit produces a slower rate over time.

Should I eat back the calories I burn exercising?

Only if you are not losing at the rate you planned. The activity factor already carries an allowance for exercise — someone who trains three or four times a week belongs at the moderately active setting, not at sedentary plus a daily bonus. Adding burned calories on top of a level that already includes them is the most common way a deficit quietly disappears.

• A new predictive equation for resting energy expenditure in healthy individuals — Mifflin MD, St Jeor ST, et al. — American Journal of Clinical Nutrition, 1990
• Human energy requirements: report of a joint FAO/WHO/UNU expert consultation — Food and Agriculture Organization of the United Nations
• Steps for Losing Weight — US Centers for Disease Control and Prevention
• Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults — National Heart, Lung, and Blood Institute (US), 1998