Calorie calculator: how many calories do you need a day?

Your basal metabolic rate (BMR) is the energy your body uses at complete rest just to keep you alive: breathing, circulation, body temperature and organ function. It's the biggest part of your daily burn, about 60 to 70% for most people who sit a lot.

Your total daily energy expenditure (TDEE) adds movement, everyday activity and digesting food. Following the FAO/WHO/UNU expert report, TDEE = BMR × physical activity level (PAL). Eat about your TDEE and your weight stays roughly stable over time; eat less and you lose, eat more and you gain.

The calculator works out BMR with three formulas and shows them side by side (kg, cm, years):

• Mifflin–St Jeor (1990, recommended): men: 10 × kg + 6.25 × cm − 5 × age + 5; women: the same − 161. A 2005 review by Frankenfield and colleagues found it the most accurate predictor of measured resting energy use, within 10% for about 70 to 80% of adults.
• Harris–Benedict, revised (Roza and Shizgal, 1984): an updated version of the classic 1919 equation. It tends to come out a little higher than Mifflin.
• Katch–McArdle: 370 + 21.6 × lean body mass (kg). It uses body composition instead of weight, so it can be more accurate for muscular, athletic people. It needs your body fat percentage; without it, we use Mifflin.

All three were built for healthy adults. Needs are different in pregnancy, while breastfeeding, with illness and under 18.

Activity is the biggest source of error, because most of us overestimate it. That's why each level is described in minutes, matched to FAO/WHO/UNU PAL values:

Level	PAL	What it means
Sedentary	1.4	desk job, under 30 minutes of walking a day, no workouts
Lightly active	1.55	30–45 minutes of walking a day, or about 150 minutes of moderate exercise a week
Moderately active	1.75	about 60 minutes of moderate activity a day, or on your feet at work with lots of walking
Very active	2.0	60–90 minutes of exercise a day, or heavy physical work
Extremely active	2.2	2 hours or more of hard training a day, competitive sport

The result shows your TDEE at all five levels in one table, so you can see what one step up or down means. If you're unsure, pick the lower one.

A 35-year-old woman, 5 ft 5 in (165 cm), 150 lb (68 kg), lightly active:

Formula	BMR	TDEE (× 1.55)
Mifflin–St Jeor	1,375 cal	2,132 cal
Harris–Benedict (revised)	1,436 cal	2,226 cal
Katch–McArdle (30% body fat)	1,398 cal	2,167 cal

Her Mifflin TDEE is about 2,130 calories, or about 8,920 kJ. With a balanced split (20% protein, 50% carbs, 30% fat), that's about 107 g protein, 266 g carbs and 71 g fat a day. For mild weight loss (−10%) her target would be about 1,920 calories, and for weight loss (−20%) about 1,705. Both stay above the safe minimum.

The calculator shows four goals: maintain, mild weight loss (−10%), weight loss (−20%) and slow gain or muscle building (+10%). For each one it works out grams of protein, carbs and fat with the split you choose:

Split	Protein	Carbs	Fat
Balanced	20%	50%	30%
Higher protein	30%	40%	30%
Lower carb	30%	30%	40%

The balanced split fits fully within the ranges set by the National Academies (protein 10–35%, carbs 45–65%, fat 20–35%). The higher-protein and lower-carb splits go below the 45% carb minimum (and lower carb puts fat above 35%), so choose them on purpose. If a goal would drop below the safe minimum (1,200 calories for women, 1,500 for men, and never below your BMR), you'll see a warning. For more detail, try the macro calculator and the protein calculator.

Every formula is an estimate: two people with the same stats can differ by 10 to 20%. Your own numbers are the most accurate. Track what you eat for 2 to 4 weeks and weigh yourself regularly (ideally every morning at the same time, and look at the weekly average).

In refine mode, enter your average daily intake, your weight change and the number of days. Real TDEE = average intake − weight change × 7,700 ÷ days (that's 3,500 calories per pound). For example, if you averaged 2,000 calories a day for 28 days and lost 2.6 lb (1.2 kg), your real TDEE is about 2,330 calories.

In the first week or two, much of the change is water, so use at least 14 days. To lose weight, the calorie deficit calculator plans week by week toward a goal date.