What This Calculator Does

"How many calories should I eat in a day?" depends on more than just body size — age, sex, and how active you are all shift the number meaningfully. This tool takes those factors and estimates your Total Daily Energy Expenditure: roughly how many calories your body burns in a day at your current activity level, which is the number most people use as a baseline before deciding whether to eat more, less, or the same.

How to Use It

Fill in your Age, Gender, Weight in kilograms, and Height in centimeters — note that height here is centimeters, not meters like the BMI Calculator, so a 175cm person enters 175, not 1.75. Then choose the Activity Level that best matches your week, from Sedentary up through Super Active, and the result gives your estimated daily calorie needs in kcal, rounded to the nearest whole calorie.

The Formula

This calculator uses the Mifflin-St Jeor equation, generally considered one of the more accurate BMR formulas for the general population. It first estimates your Basal Metabolic Rate — the calories you'd burn lying still all day — and the formula differs slightly by gender: for men, BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women, BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161.

That BMR is then multiplied by an activity factor to reach TDEE: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, and 1.9 for super active (very hard exercise or a physical job, on top of intense training). The final TDEE figure is rounded to the nearest whole calorie.

A Worked Example

A 30-year-old male, 70kg, 175cm, moderately active: BMR = (10 × 70) + (6.25 × 175) − (5 × 30) + 5 = 700 + 1093.75 − 150 + 5 = 1648.75. Multiply by the moderate-activity factor of 1.55 and TDEE = 1648.75 × 1.55 = 2555.5625, which rounds to 2,556 kcal per day. For contrast, a 25-year-old female, 60kg, 165cm, sedentary: BMR = (10 × 60) + (6.25 × 165) − (5 × 25) − 161 = 600 + 1031.25 − 125 − 161 = 1345.25, and at the sedentary multiplier of 1.2, TDEE = 1345.25 × 1.2 = 1614.3, rounding to 1,614 kcal per day — noticeably lower, driven by both the smaller body size and the much lower activity multiplier.