Calorie and Macro Calculator

Example Calculation

A 30-year-old woman, 5 feet 6 inches tall and 150 pounds, with 1 to 3 workouts a week, has a resting burn (BMR) of about 1,417 calories. With light activity (x 1.375) her maintenance level is about 1,949 calories a day.

On a balanced 40/30/30 split, that is roughly 195 g of carbs, 146 g of protein and 65 g of fat. To lose about half a pound a week, she would aim near 1,699 calories.

How It Works

This calculator estimates how many calories your body burns each day and turns that number into a practical eating target. It starts with your basal metabolic rate (BMR) — the energy your body needs at rest — using the Mifflin-St Jeor equation, which research has found to be one of the more reliable predictive formulas for most adults.

Next, your BMR is multiplied by an activity factor ranging from 1.2 for a sedentary lifestyle to 1.9 for very hard daily training. The result is your total daily energy expenditure (TDEE), the estimated calories needed to maintain your current weight. To lose weight, the tool subtracts calories; to gain, it adds them. As a rough guide, a daily change of about 500 calories corresponds to around one pound per week, though real-world results vary with metabolism, adherence and water weight.

Finally, your calorie target is split into macronutrients. Protein and carbohydrates provide 4 calories per gram and fat provides 9 calories per gram. Pick a macro split — balanced, high protein, low carb or higher carb — and the tool converts percentages into grams you can track. Higher protein intake can help preserve muscle during weight loss, while carbohydrates fuel high-intensity training.

The calculator sets a safety floor of 1,200 calories for women and 1,500 for men so aggressive goals do not drop below commonly recommended minimums. Treat the numbers as a starting point: track your weight and energy for two to three weeks, then adjust by 100–200 calories if progress stalls. Anyone with a medical condition, pregnancy or a history of disordered eating should consult a clinician or registered dietitian before changing their diet.

Formula Explained

Men: BMR = 10 × kg + 6.25 × cm − 5 × age + 5. Women: BMR = 10 × kg + 6.25 × cm − 5 × age − 161.

TDEE = BMR × activity factor; Target = TDEE ± goal adjustment.

Grams: carbs and protein = calories × % ÷ 4; fat = calories × % ÷ 9.

Assumptions and limits

• The equation is 10 × weight (kg) + 6.25 × height (cm) − 5 × age, plus 5 for men or minus 161 for women. It was fitted on healthy adults aged 19 to 78 and predicts within about 10% for many people, not all.
• The activity factors (1.2 to 1.9) are standard multipliers, and choosing the level that fits you is a judgment call.
• A goal of −500 or +500 calories a day is a rule of thumb for about 1 pound a week. Real weight change slows as the body adapts.
• Targets are not allowed to fall below 1,200 calories a day for women or 1,500 for men. These floors are a common safety convention, not a medical recommendation.
• It is for healthy adults. It does not cover pregnancy, breastfeeding, medical conditions or athletes in training.