Calorie Calculator

There is no single answer, because the figure depends on your size, age, sex and how active you are. The method used here is the one the FAO/WHO/UNU expert consultation recommends for adults: estimate your resting metabolic rate — the energy you would burn lying still all day — then multiply it by a physical activity level. A 30-year-old man of 70 kg and 175 cm has a resting rate of about 1,650 kcal, and a sedentary lifestyle takes that to roughly 2,310 kcal a day.

Mifflin-St Jeor unless you have a measured body fat percentage. It was published in 1990 on a sample of 498 adults specifically to improve on the older Harris-Benedict equation, and it generally predicts a slightly lower and more realistic resting rate. Use Katch-McArdle if you know your body fat — it works from lean mass and has no sex or age term at all, which makes it the best of the three for a very lean or very muscular body. The revised Harris-Benedict is included because it is still widely quoted; it usually reads about 3% higher than Mifflin-St Jeor.

Because 1.2 is below the range the FAO/WHO/UNU consultation defines for any sustainable lifestyle. Its lowest band, "sedentary or light activity", runs from 1.40 to 1.69; a physical activity level near 1.2 describes something closer to bed rest. Even a desk job with no exercise involves standing, walking, cooking and commuting. Most calorie calculators inherited 1.2 from each other rather than from the literature, and the effect is to understate your requirement by roughly 15% — which, for a tool mostly used to plan a deficit, is the more harmful direction to be wrong in.

About 500 calories a day. The NHLBI clinical guidelines state that a deficit of 500 to 1,000 kcal a day is aimed at a loss of 1 to 2 lb a week, which is the familiar "3,500 calories to a pound" expressed as a rate. Treat it as a starting point rather than a law. A lighter body burns less, so a constant deficit produces a loss that slows over time instead of continuing in a straight line, and projecting this arithmetic out over a year will overstate what actually happens.

It is an estimate, and the error at the individual level is real. Predictive equations are regressions fitted to a sample, so they describe the average person of your measurements rather than you: two people of identical height, weight, age and sex can differ in resting rate by a couple of hundred calories. The right way to use this number is as an opening hypothesis — eat to it for two or three weeks, track your weight, and adjust by what actually happened rather than by what the equation predicted.

The 2013 AHA/ACC/TOS obesity guideline describes prescribed low-calorie targets of 1,200 to 1,500 kcal a day for women and 1,500 to 1,800 for men. This calculator still shows you a goal that falls below those figures, because hiding it would be worse, but it labels it. Aggressive deficits reach very low intakes quickly on a smaller body — a sedentary 70-year-old woman aiming to lose 2 lb a week lands around 640 kcal a day, which is not a diet anyone should design for themselves. Below those thresholds it becomes hard to meet protein and micronutrient needs, and that is a conversation for a doctor or dietitian.

No. Every equation offered here was derived on adults, which is why the age field starts at 18. Children and adolescents are still growing, so their requirements are banded by age and growth stage and are not a simple function of body size. Pregnancy and breastfeeding both add a substantial requirement on top of the figures shown here. In all three cases the number this calculator produces is the wrong model, not merely an imprecise one.