Calorie Calculator

Understanding Calories and Metabolism

A calorie is a unit of energy. When we talk about "calories" in food and nutrition, we mean kilocalories (kcal) — the energy required to raise 1 litre of water by 1°C. Your body uses calories constantly: even at complete rest, your organs consume energy to maintain basic functions like breathing, circulation, and cell repair.

Basal Metabolic Rate (BMR)

BMR is the number of calories your body burns at complete rest over 24 hours. This calculator uses the Mifflin-St Jeor equation, the most accurate formula for most adults:

Male: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5

Female: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161

Total Daily Energy Expenditure (TDEE)

TDEE = BMR × Activity Multiplier. The multiplier ranges from 1.2 (sedentary) to 1.9 (extremely active). TDEE represents how many calories you need to maintain your current weight given your lifestyle.

Macros for Your Goal

Macronutrients — protein, carbohydrates, and fat — provide the calories in food. The optimal split depends on your goal:

• Weight loss: TDEE − 500 kcal/day → lose ~0.5 kg/week. Higher protein (30–35%) preserves muscle during a deficit.
• Maintenance: Eat at TDEE. Balanced macro split around 25% protein / 45% carbs / 30% fat.
• Muscle gain: TDEE + 300 kcal/day. Prioritise protein (30–35%) and higher carbohydrates for training fuel.

A Note on Accuracy

Formulas give estimates. Individual metabolism varies due to genetics, gut microbiome, hormones, and sleep. Track your weight for 2–3 weeks and adjust intake by 100–200 kcal if your weight isn't moving in the expected direction.