How to use the calorie calculator
- Enter your details. Pick US or metric units, then add your sex, age, height and current weight. The calculator is for adults 18 and over.
- Choose your activity level. Be honest: most people with a desk job and a few workouts a week are light, not moderate.
- Pick your goal. Lose, lose slowly, maintain or gain. Losing sets a target about 20 percent below maintenance.
- Read your target and macros. See your BMR, your maintenance calories (TDEE), your daily target and protein, carbs and fat in grams.
How the calorie calculator works
First we estimate your basal metabolic rate (BMR), the energy your body burns at complete rest, using the Mifflin St Jeor equation. Published in 1990 and recommended by the Academy of Nutrition and Dietetics, it is one of the most accurate simple formulas for healthy adults:
- Men: 10 x weight (kg) + 6.25 x height (cm) minus 5 x age + 5
- Women: 10 x weight (kg) + 6.25 x height (cm) minus 5 x age minus 161
Then we multiply BMR by an activity factor to get your total daily energy expenditure (TDEE), the calories you burn in a typical day. Eating around your TDEE keeps your weight steady. Eating less leads to weight loss, and eating more leads to gain.
Activity levels explained
| Activity level | Multiplier | Typical week |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Light | 1.375 | Exercise 1 to 3 days a week |
| Moderate | 1.55 | Exercise 3 to 5 days a week |
| Very active | 1.725 | Hard exercise 6 to 7 days a week |
| Athlete | 1.9 | Physical job plus training |
Most people overestimate how active they are. If you are unsure, pick the lower level and adjust after a few weeks.
How many calories to lose weight
A deficit of about 20 percent below maintenance gives steady loss of roughly 0.5 to 1 kg (1 to 2 lb) a week for most people, the pace health agencies such as the CDC describe as sustainable. Bigger deficits often backfire with hunger, muscle loss and fatigue. We never suggest going below 1,200 kcal for women or 1,500 kcal for men without medical supervision.
Worked example: 35, 5 ft 6 in, 165 lb, lightly active
Here is a real run of the calculator for a 35 year old woman who is 5 ft 6 in (168 cm), weighs 165 lb (74.8 kg) and exercises one to three days a week, with the goal of losing weight.
| Step | Working | Result |
|---|---|---|
| BMR (Mifflin St Jeor) | 10 x 74.8 + 6.25 x 167.6 − 5 x 35 − 161 | 1,460 kcal |
| Maintenance (TDEE) | 1,460 x 1.375 for light activity | 2,008 kcal |
| Target to lose weight | 2,008 x 0.8, rounded | 1,610 kcal |
| Daily macros | Protein first, 30 percent fat, carbs make up the rest | 141 g protein, 140 g carbs, 54 g fat |
That target is about 400 calories a day below maintenance. Her BMR of 1,460 is also the answer to "how many calories do I burn a day doing nothing": it is what her body uses at complete rest.
How many calories a day for women and men, by age
Real runs of the calculator at a steady weight. At the same size, BMR drops by 50 calories a day for every 10 years of age, so maintenance falls by about 60 to 80 calories a day each decade.
Women, 5 ft 4 in (163 cm), 140 lb (63.5 kg):
| Age | Sedentary | Light | Moderate | To lose weight (light) |
|---|---|---|---|---|
| 25 | 1,638 | 1,877 | 2,116 | 1,500 |
| 35 | 1,578 | 1,808 | 2,038 | 1,450 |
| 45 | 1,518 | 1,739 | 1,961 | 1,390 |
| 55 | 1,458 | 1,671 | 1,883 | 1,340 |
| 65 | 1,398 | 1,602 | 1,806 | 1,280 |
Men, 5 ft 10 in (178 cm), 180 lb (81.6 kg):
| Age | Sedentary | Light | Moderate | To lose weight (light) |
|---|---|---|---|---|
| 25 | 2,169 | 2,486 | 2,802 | 1,990 |
| 35 | 2,109 | 2,417 | 2,724 | 1,930 |
| 45 | 2,049 | 2,348 | 2,647 | 1,880 |
| 55 | 1,989 | 2,279 | 2,569 | 1,820 |
| 65 | 1,929 | 2,211 | 2,492 | 1,770 |
The weight loss column is 20 percent below light activity maintenance, which is a deficit of about 320 to 380 calories a day for these women and 440 to 500 for these men.
How many calories to gain weight
To gain, eat a little above maintenance and keep protein up. "Gain slowly" adds 10 percent, which suits building lean muscle; "Gain weight" adds 15 percent.
| Person | Maintenance | Gain slowly | Gain weight |
|---|---|---|---|
| Woman, 25, 5 ft 4 in, 110 lb, light activity | 1,690 | 1,860 (+170) | 1,940 (+250) |
| Man, 25, 5 ft 10 in, 150 lb, moderate activity | 2,591 | 2,850 (+259) | 2,980 (+389) |
Weigh yourself weekly. If the scale has not moved after 3 weeks, add another 100 to 200 calories a day.
Why the numbers are estimates
Formulas predict averages. Genetics, muscle mass, hormones, medications and sleep all shift real calorie needs by 10 percent or more. Use the result as a starting point, weigh yourself a few times a week and look at the trend over two to three weeks before adjusting. Pair it with the weight loss calculator to see a timeline, or the keto macro calculator if you prefer low carb. For more everyday wellness reading, visit Suddl.
Sources: Mifflin MD, St Jeor ST et al., Am J Clin Nutr 1990; Academy of Nutrition and Dietetics; CDC guidance on healthy weight loss.
