How the calorie calculator works
Your daily calorie need starts with your basal metabolic rate (BMR) — the energy your body uses at rest. This tool uses the Mifflin-St Jeor equation, the most accurate of the common formulas:
BMR = 10·weight(kg) + 6.25·height(cm) − 5·age + s
where s is +5 for men and −161 for women. Multiplying BMR by an activity factor gives your total daily energy expenditure (TDEE) — the calories needed to maintain your weight.
Activity multipliers
- Sedentary (×1.2): desk job, little exercise
- Light (×1.375): light exercise 1–3 days/week
- Moderate (×1.55): exercise 3–5 days/week
- Active (×1.725): hard exercise 6–7 days/week
- Very active (×1.9): intense training or a physical job
Eating to lose or gain weight
A pound of body fat holds roughly 3,500 calories, so a daily deficit of 500 calories trims about a pound a week. To gain, add calories instead. The targets above apply that math to your TDEE — but they're starting points. Track your weight for two to three weeks and adjust if the trend isn't matching your goal.
A quick example
A 30-year-old man, 175 cm and 75 kg, exercising moderately, has a BMR around 1,699 and a TDEE near 2,633 calories. To lose about a pound a week he'd aim for roughly 2,133 calories a day; to gain, he'd eat above 2,633.
Frequently asked questions
How are daily calorie needs calculated?
This calculator uses the Mifflin-St Jeor equation to estimate your basal metabolic rate (BMR) — the calories you burn at rest — then multiplies by an activity factor to get your total daily energy expenditure (TDEE), the calories needed to maintain your current weight.
What is the difference between BMR and TDEE?
BMR is the energy your body uses at complete rest just to stay alive. TDEE is BMR plus the calories you burn through daily activity and exercise. TDEE is the more useful number for planning meals, since it reflects how much you actually need each day.
How many calories should I eat to lose weight?
A deficit of about 500 calories below your TDEE per day leads to roughly one pound of fat loss per week, since a pound is about 3,500 calories. A 1,000-calorie deficit targets about two pounds a week. Avoid going too low — very aggressive deficits are hard to sustain and can cost muscle.
Are these calorie numbers exact?
No. They are well-validated estimates, but real needs vary with genetics, body composition, hormones, and how accurately you judge your activity level. Use the result as a starting point, then adjust based on how your weight actually changes over a few weeks.
Source: Daily calorie needs use the Mifflin-St Jeor equation for basal metabolic rate, from Mifflin et al. (1990), American Journal of Clinical Nutrition, with standard activity multipliers applied to estimate TDEE. Last reviewed June 2026 by the CalcQuill editorial team.
Disclaimer: Calorie estimates are for general informational purposes only and are not medical or nutritional advice. Consult a healthcare professional before starting a diet or exercise program.