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.
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.
