How many calories do I need? BMR and TDEE explained

Your daily calorie need is your total daily energy expenditure (TDEE): the energy your body uses at rest, called basal metabolic rate (BMR), plus the energy you use moving, exercising and digesting food. The usual way to estimate it is to calculate BMR from your sex, age, height and weight, then multiply by an activity factor. A calculator does this in seconds, and the steps below show how to check it by hand.

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What BMR and TDEE measure

BMR is the energy your body needs to keep running while you lie still: breathing, circulating blood, keeping your temperature steady. TDEE adds everything you do on top of that. For planning food, TDEE is the figure that matters, because eating roughly that much keeps your weight steady over time.

Both numbers are estimates. Two people of the same age, height and weight can burn different amounts, so a formula can be a few hundred calories a day off for an individual.

The Mifflin-St Jeor equation

Mifflin and St Jeor published this equation in the American Journal of Clinical Nutrition in 1990. It was derived from 498 healthy adults aged 19 to 78. It uses weight in kilograms, height in centimetres and age in whole years:

• Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
• Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161

Dietitians use it widely. The U.S. Academy of Nutrition and Dietetics recommends it when resting metabolic rate cannot be measured directly, and it is generally more accurate than the older Harris-Benedict equation. It is less precise at very high body weights, and its development sample did not cover a broad range of ethnic groups, so treat the result as a starting point.

Pounds and inches convert easily. Divide pounds by 2.2 to get kilograms, and multiply inches by 2.54 to get centimetres.

A worked example

Take a woman who is 35, weighs 70 kg (154 lb) and is 165 cm (5 ft 5 in) tall:

• 10 × 70 = 700
• 6.25 × 165 = 1,031.25
• 5 × 35 = 175
• 700 + 1,031.25 − 175 − 161 = 1,395.25

Her BMR is about 1,395 kcal per day.

Multiply by an activity factor

Most calculators multiply BMR by one of these conventional factors:

Activity level	Factor	Typical week
Sedentary	1.2	Little or no exercise
Lightly active	1.375	Light exercise 1 to 3 days
Moderately active	1.55	Moderate exercise 3 to 5 days
Very active	1.725	Hard exercise 6 to 7 days
Extra active	1.9	Very hard exercise or a physical job

The factors are conventions, not measurements. Pick the level that matches an ordinary week, not your best one. Continuing the example, 1,395 × 1.55 gives about 2,163 kcal per day for a moderately active woman.

Calories for losing, keeping or gaining weight

Eat below your TDEE to lose weight, and above it to gain. The traditional rule says a deficit of 3,500 kcal (about 7,700 kcal per kilogram) removes one pound of fat. A deficit of 500 kcal a day, which is 3,500 a week, therefore predicts about one pound a week. The rule traces back to a 1958 estimate. Kevin Hall's 2008 paper on energy deficit per unit of weight loss shows that it is only a rough guide, because the body adjusts as it loses weight.

For a realistic pace, the NHS advises aiming to lose 1 to 2 lb, or 0.5 to 1 kg, a week. Using the example above, a 500 kcal deficit gives a target of about 1,663 kcal per day, which should lose roughly half a kilogram a week at first. Losses slow down as body weight falls, so review the target every few weeks.

Do not set an intake far below your TDEE without advice from a doctor or dietitian.

Splitting calories into macros

Protein and carbohydrate supply 4 kcal per gram, and fat supplies 9 kcal per gram, the factors used on nutrition labels. To turn a daily target into grams, multiply the calories by the share you want, then divide by the factor. At 1,663 kcal with protein at 30 percent: 1,663 × 0.30 = 499 kcal, and 499 ÷ 4 = about 125 g of protein.

Mistakes that throw the number off

• Entering pounds into a kilogram field, or inches into a centimetre field. This can change the result by a large margin.
• Choosing a high activity level because of one hard workout.
• Trusting package calorie counts to the last calorie. Labels are approximate.
• Forgetting to recalculate after a large change in weight.

Quick answers

Is BMR the same as TDEE? No. BMR is the energy used at rest. TDEE is BMR multiplied by an activity factor, so it is always higher.

Why not just use 2,000 calories? Needs vary by size, age, sex and activity. A fixed figure can be far too high or too low for you.

Does the calculator work for children or pregnant people? Not reliably. The equation is for adults, and pregnancy and breastfeeding change energy needs.

How often should I recalculate? When your weight changes by a noticeable amount, or when your activity changes.

This is general information, not medical advice. Ask a doctor or registered dietitian before a large calorie deficit, if you have a medical condition or take medication that affects weight, or if you are under 18.

For a quick check of your weight category, use the BMI calculator and read the adult BMI categories. BMI is a rough screening measure and does not replace this calculation.