Understanding Calories — How Many Do You Really Need?
Calories are the units of energy your body uses to perform every function — from breathing and circulation to exercise and digestion. Your Total Daily Energy Expenditure (TDEE) represents the total number of calories your body burns in a day, accounting for your resting metabolism and all physical activity. Understanding your TDEE is the foundation of any effective weight management strategy. Eating below your TDEE creates a calorie deficit for weight loss; eating above it creates a surplus for muscle gain. This calculator uses the Mifflin-St Jeor equation, published in 1990 and validated across diverse populations, which is considered the most accurate formula for estimating BMR in the general population. The formula takes into account your weight, height, age, and sex to estimate your resting calorie burn, which is then multiplied by an activity factor to give your TDEE.
Frequently Asked Questions
What is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain basic life functions — breathing, circulation, cell production, and temperature regulation. It represents approximately 60–75% of total daily calorie expenditure for most people.
What is the Mifflin-St Jeor formula?
The Mifflin-St Jeor equation (1990) is widely considered the most accurate BMR formula for the general population. For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161.
How accurate is a calorie calculator?
Calorie calculators provide estimates, not exact figures. Individual variations in metabolism, gut microbiome, hormone levels, and body composition mean actual needs can vary by 10–20% from calculated values. Use the result as a starting point and adjust based on real-world results over 2–4 weeks.
How many calories should I eat to lose weight?
A deficit of 500 calories per day below your TDEE typically produces approximately 0.5 kg (1 lb) of fat loss per week. A 1,000 calorie deficit targets roughly 1 kg per week. Do not go below 1,200 cal/day for women or 1,500 cal/day for men without medical supervision.