How to use the Calorie Intake Calculator (Simple)
Enter your sex, age, height, weight, and activity level, then pick a goal (lose, maintain, or gain weight). The calculator estimates your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, converts it to total daily energy expenditure (TDEE) using your activity multiplier, and adjusts TDEE for your goal to produce a daily calorie target plus a starting protein, carb, and fat split.
How the math works
- BMR (Basal Metabolic Rate): calories your body burns at complete rest. This calculator uses the Mifflin-St Jeor equation: 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5 for men, or -161 in place of +5 for women. It is widely regarded as one of the more accurate resting-metabolism formulas for the general adult population.
- TDEE (Total Daily Energy Expenditure): BMR × activity multiplier. Sedentary desk work uses about 1.2×, light exercise (1-3 days/week) about 1.375×, moderate exercise (3-5 days/week) about 1.55×, hard training (6-7 days/week) about 1.725×, and very hard daily training about 1.9×.
- Daily calorie target: TDEE plus the calorie adjustment for your goal. A 500 kcal/day deficit or surplus approximates 1 lb of weekly weight change, and a 250 kcal/day adjustment approximates half that rate, using the common rule that 1 lb of body fat represents about 3,500 kcal.
- Macronutrients: protein is set at 1.6 g per kg of body weight to help preserve lean mass; fat is set at 25% of the calorie target (9 kcal/g); the remaining calories become carbohydrates (4 kcal/g).
Common calibration mistakes
- Overestimating activity level - many people select "moderate" or "active" when their true weekly exercise volume is closer to sedentary or light.
- Tracking calories burned from exercise and adding them back to the daily target - the activity multiplier already accounts for typical exercise. Adding exercise calories on top can create an unintended surplus.
- Treating the output as exact. Use it as a starting point for 2-3 weeks, then adjust the calorie target up or down based on your observed weight trend.
Frequently Asked Questions
What formula does this calorie calculator use?
This calculator estimates basal metabolic rate (BMR) with the Mifflin-St Jeor equation: 10 x weight in kg + 6.25 x height in cm - 5 x age + 5 for men, or -161 in place of +5 for women. BMR is multiplied by an activity factor (1.2 to 1.9) to estimate total daily energy expenditure (TDEE), and your selected goal then adjusts TDEE up or down to set a daily calorie target.
How much should I eat to lose or gain weight?
A sustained deficit of about 500 kcal per day below maintenance is roughly 1 lb of weight loss per week, using the approximation that 1 lb of body fat represents about 3,500 kcal. The same math applies in reverse for a surplus and weight gain. Very large deficits or surpluses are harder to sustain and can affect energy levels and lean mass.
How are the protein, carb, and fat targets calculated?
Protein is set at 1.6 grams per kilogram of body weight, a level commonly used to help preserve lean mass during a calorie deficit. Fat is set at 25 percent of the daily calorie target divided by 9 kcal per gram. The remaining calories are assigned to carbohydrates at 4 kcal per gram.