What is BMR (Basal Metabolic Rate)?

BMR is the number of calories your body burns at complete rest to maintain essential physiological functions — breathing, circulation, cell repair and temperature regulation. It represents the minimum calorie intake needed to keep your body alive.

How is BMR calculated?

GoChronos uses the Mifflin-St Jeor equation, the most accurate widely-used formula: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5 for males, or − 161 for females. It is more accurate than the older Harris-Benedict formula.

TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, including BMR plus calories burned through activity and digestion. It is calculated by multiplying BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active).

How many calories do I need per day?

Your daily needs equal your TDEE. For maintenance eat at TDEE; for weight loss create a deficit of 300–500 calories; for muscle gain add 300–500 calories above TDEE.

What are macros and how are they calculated?

Macros (macronutrients) are protein, carbohydrates and fat. A common starting split is 30% protein / 40% carbs / 30% fat. The calculator converts your calorie target into grams of each macro (protein: 4 cal/g, carbs: 4 cal/g, fat: 9 cal/g).

Is it safe to eat below my BMR?

Consistently eating below your BMR is not recommended: it can slow metabolism, cause muscle loss and lead to nutritional deficiencies. Safe calorie restriction means eating below your TDEE maintenance level, not below your BMR.

Is the metabolic calculator free?

Yes. Completely free, runs in your browser, no sign-up required. Your health data is never transmitted to any server.

Metabolic Calculator — BMR, TDEE & Calories

All-in-one metabolic calculator: basal metabolic rate (BMR), total daily energy expenditure (TDEE) and calorie & macro targets for any goal.