How to use the calorie calculator
- Choose Male or Female and enter your Age.
- Pick US (ft, in, lb) or Metric (cm, kg), then enter your Height and Weight. Your numbers convert when you switch.
- Choose your Activity level.
- Read your BMR, your TDEE, and the calorie target for each goal. Everything updates as you change a field.
How the numbers are worked out
Your BMR comes from the Mifflin-St Jeor equation (1990), with weight in kilograms and height in centimeters:
- Men: BMR = 10 × weight + 6.25 × height - 5 × age + 5
- Women: BMR = 10 × weight + 6.25 × height - 5 × age - 161
The paper's exact coefficients are 9.99 and 4.92; the rounded 10 and 5 used here change the result by only a few calories. TDEE is BMR times the activity factor: 1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 very active, 1.9 extra active. The goal rows add or subtract 250 or 500 calories, roughly half a pound or a pound a week by the 3,500 calories per pound rule.
Worked example
The starting inputs are a 30-year-old man, 5 ft 10 in (177.8 cm), 175 lb (79.38 kg), lightly active. BMR = 10 × 79.38 + 6.25 × 177.8 - 5 × 30 + 5 = 1,760. TDEE = 1,760 × 1.375 = 2,420. The targets are 1,920 to lose about a pound a week, 2,170 to lose half a pound, 2,670 to gain half a pound, and 2,920 to gain a pound. In the example macro table, the maintenance row shows 182 g protein, 242 g carbs, and 81 g fat.
Limits and edge cases
Treat the result as an estimate. Muscle mass, genetics, medications, and health conditions can move real needs well away from the formula. The equation was built from adults aged 19 to 78, so the tool adds a note for ages under 19 and over 78. It accepts ages 15 to 100.
The 3,500 calories per pound rule is a short-term guide, because your body adapts as you lose weight. The NIH Body Weight Planner models that slowdown. A weight-loss row under 1,500 calories for men or 1,200 for women is flagged with a warning rather than changed, so check with a doctor or dietitian first.
To turn calories into grams of protein, carbs, and fat, use the macro calculator. To plan a goal date, try the weight loss calculator. To count calories a workout burns, use the calorie burn calculator, and to see where your weight sits, the BMI calculator. More detail: how to calculate your TDEE.
Frequently asked questions
How many calories should I eat a day?
It depends on your size, age, sex, and activity. This calculator estimates your TDEE, the calories that keep your weight steady. Eating about 250 to 500 calories below it is a common way to lose weight gradually, and above it a common way to gain.
What is the difference between BMR and TDEE?
BMR is the calories your body burns at complete rest. TDEE is your BMR times an activity factor, so it also counts walking, exercise, and everyday movement. TDEE is the number to use when planning how much to eat.
How accurate is the Mifflin-St Jeor equation?
Studies find it predicts resting metabolic rate within about 10% of measured values for most adults, and it beats older equations such as Harris-Benedict. Your own metabolism can still differ, so treat the result as a starting point.
Does eating 500 fewer calories really mean losing a pound a week?
It is a rough guide. The 3,500 calories per pound rule ignores that your body adapts as you lose weight, so it overestimates loss over time. Track your weight for two to four weeks and adjust.
Which activity level should I choose?
Choose the level that matches your usual week, not your best week, because most people overestimate. If you are unsure, start with Light and adjust after two to four weeks of real results.
Sources: Mifflin et al., Am J Clin Nutr 1990; Why is the 3500 kcal per pound rule wrong? (PMC); NIDDK Body Weight Planner. Not medical advice.