Calorie & TDEE Calculator
Find out how many calories you burn each day and how many you need to maintain, lose, or gain weight. Uses the Mifflin-St Jeor equation, recommended by the Academy of Nutrition and Dietetics.
How Calorie & TDEE Calculator works
BMR — Basal Metabolic Rate
BMR is the number of calories your body burns at complete rest to maintain basic functions — breathing, circulation, cell production, and temperature regulation. It accounts for roughly 60–75% of total daily calorie expenditure. The Mifflin-St Jeor equation (1990) is the most widely recommended formula for estimating BMR, more accurate than the older Harris-Benedict equation for most people.
TDEE — Total Daily Energy Expenditure
TDEE is your total calorie burn over a day, accounting for physical activity. It is calculated by multiplying BMR by an activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725), and extra active (1.9). These multipliers are approximate — individual metabolism varies, and "activity level" is inherently imprecise.
Weight change and calorie balance
One kilogram of body fat stores approximately 7,700 kilocalories of energy. A daily deficit of 550 kcal (half a kilogram of fat per week) or a surplus of 550 kcal should theoretically produce the corresponding weight change. In practice, the body adapts to sustained deficits through reduced metabolic rate and changes in activity, making actual weight loss slower than the arithmetic suggests over longer periods.
Limitations
These figures are estimates. Individual BMR can vary by up to 20% from the formula prediction due to genetics, hormones, lean muscle mass, and health conditions. People with thyroid disorders, insulin resistance, or polycystic ovary syndrome may find their actual needs differ significantly. For weight management beyond general guidance, a registered dietitian can provide personalised assessment.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is the calories you burn if you lay still all day — your body's minimum energy requirement to keep functioning. TDEE adds the calories burned through activity (exercise, walking, daily movement). TDEE is the number you compare against food intake to determine whether you're in a calorie surplus, deficit, or balance.
How accurate is the Mifflin-St Jeor equation?
The Mifflin-St Jeor equation predicts BMR within about 10% for most adults. It is more accurate than the Harris-Benedict equation for most body types. Highly muscular people will have higher actual BMRs than predicted (muscle burns more calories than fat), and very sedentary people may have lower actual TDEEs than the multipliers suggest.
How many calories should I eat to lose weight?
A modest deficit of 300–500 kcal per day typically produces 0.3–0.5 kg of weight loss per week without feeling overly restricted. Deficits larger than 1,000 kcal per day are generally not recommended for unsupervised weight loss as they risk muscle loss and nutritional deficiencies. The NHS recommends a target of no less than 1,200 kcal/day for women and 1,500 kcal/day for men.
Do I need to count calories to lose weight?
Not necessarily. Many people achieve sustainable weight loss by changing food quality, portion awareness, and eating habits without tracking every calorie. Calorie counting is a tool that works well for some people and poorly for others. The most effective approach is one you can sustain long-term.
This calculator provides estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.