How many calories do you need?
Your body burns energy all day, even while you sleep. The calories you need per day to keep your weight steady are your maintenance calories, or TDEE (total daily energy expenditure). Eat less than that and you lose weight, eat more and you gain. This calorie calculator estimates the number from your sex, age, height, weight and activity level, then shows targets for weight loss and weight gain.
The formula: Mifflin-St Jeor
First the calculator works out your BMR, the basal metabolic rate, with the Mifflin-St Jeor equation. It is the formula most dietitians use for adults today. Then it multiplies the BMR by an activity factor to get your TDEE.
Example: a 30 year old man, 5 ft 10 in (177.8 cm) and 180 lb (81.6 kg), has a BMR of about 1,783 kcal. Moderately active, that is 1,783 × 1.55 = about 2,763 kcal a day to maintain his weight.
Activity level factors
| Activity level | Factor | What it means |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise. |
| Lightly active | 1.375 | Light exercise or sports 1 to 3 days a week, or a job with some walking. |
| Moderately active | 1.55 | Moderate exercise 3 to 5 days a week. |
| Very active | 1.725 | Hard exercise 6 to 7 days a week, or a physical job. |
| Extra active | 1.9 | Very hard training twice a day, or hard physical work plus training. |
Calorie deficit and surplus
A pound of body fat holds roughly 3,500 kcal. A daily deficit of 500 kcal adds up to about 3,500 kcal a week, or 1 lb of weight loss. A surplus works the same way for weight gain. Real results drift from this rule after a few weeks, because a lighter body burns less, so recheck your numbers every 10 to 15 lb.
- Lose 0.5 lb a week: eat 250 kcal less per day. Easy to stick with.
- Lose 1 lb a week: 500 kcal less per day. A common, sustainable pace.
- Lose 2 lb a week: 1,000 kcal less per day. Fast, and only sensible with a lot of weight to lose.
- Gain 0.5 to 1 lb a week: 250 to 500 kcal more per day, ideally with strength training so most of the gain is muscle.
Women should not go below about 1,200 kcal and men below about 1,500 kcal a day without medical supervision. The calculator marks goals under those limits.
Protein and macros
Calories are only part of the picture. While losing weight, enough protein helps you keep muscle and feel full. A common target for active people is 0.7 to 1 g of protein per pound of body weight (1.6 to 2.2 g per kg). Split the remaining calories between carbs and fat in a way you can keep up. Protein and carbs have about 4 kcal per gram, fat about 9.
How to use the calorie calculator
- 1Pick US or metric units and your sex.
- 2Enter your age, height and weight, then choose the activity level that fits a normal week.
- 3Read your maintenance calories and the targets to lose or gain weight. Track your weight for a few weeks and adjust by 100 to 200 kcal if needed.
Frequently asked questions
How many calories should I eat per day?
About as many as you burn, if you want to keep your weight. That number is your maintenance calories, also called TDEE. To lose weight, eat less than that, to gain, eat more. A deficit of 500 calories a day leads to roughly 1 lb of weight loss a week for most people.
What is the difference between BMR and TDEE?
BMR, the basal metabolic rate, is what your body burns at complete rest to keep you alive: breathing, circulation, body temperature. TDEE, total daily energy expenditure, adds everything you do on top, from walking to training. TDEE is BMR times an activity factor.
How accurate is this calorie calculator?
The Mifflin-St Jeor equation is one of the most accurate formulas for healthy adults, usually within about 10% of a lab measurement. Your real needs can still differ. Track your weight for 2 to 3 weeks at the suggested intake and adjust by 100 to 200 calories if it moves in the wrong direction.
Which activity level should I pick?
Most people overestimate their activity. If you work at a desk and exercise 3 times a week, lightly active is usually closer than moderately active. When in doubt, pick the lower level, then adjust after a few weeks of tracking.
Why does the calculator flag some goals?
Eating under about 1,200 calories a day for women or 1,500 for men makes it hard to get enough protein, vitamins and minerals, and can cost muscle. Very low calorie diets should only be done with a doctor or dietitian. The calculator shows those numbers but marks them as not recommended.