Calorie Calculator

Your daily calorie need depends on age, sex, height, weight, and activity level. The average adult male needs about 2,400-3,000 kcal/day to maintain weight, and the average adult female needs 1,800-2,400 kcal/day. This calorie calculator personalises the number for you using the Mifflin-St Jeor equation, which is widely considered the most accurate BMR predictor for the general population.

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest to keep you alive — breathing, circulating blood, maintaining body temperature. TDEE (Total Daily Energy Expenditure) is BMR plus all the calories you burn through daily activity, exercise, digestion, and fidgeting (NEAT). TDEE = BMR × activity multiplier. Eating at your TDEE maintains weight; below it loses weight; above it gains weight.

One pound of body fat stores roughly 3,500 kcal. To lose 1 lb of fat per week you need a cumulative deficit of 3,500 kcal — about 500 kcal/day below your TDEE. This is the sweet spot for sustainable fat loss: aggressive enough to see progress, gentle enough to preserve muscle, energy, and mood. Faster targets (1,000 kcal/day deficit for ~2 lb/wk) are possible but tend to cause muscle loss, hunger, and rebound weight gain when the diet ends.

Yes — the 2005 ADA meta-analysis found Mifflin-St Jeor predicts BMR within ±10% of measured values for most non-obese adults, outperforming Harris-Benedict (1919/1984), Schofield (1985), and Owen formulas. For very lean athletes (men under 12% body fat, women under 18%) the Katch-McArdle equation, which uses lean body mass, can be more accurate. For people with significant obesity (BMI 40+) results may overestimate by 5-15%, since BMR per kg drops at extreme weights.

Be honest — most people overestimate by one bracket. 1.2 Sedentary: desk job, almost no exercise. 1.375 Lightly active: light exercise or sports 1-3 days/week. 1.55 Moderately active: moderate exercise 3-5 days/week — this is the most common bracket. 1.725 Very active: hard exercise or sports 6-7 days/week. 1.9 Extra active: very hard daily training, physical job, or two-a-day workouts. If you have a desk job and lift weights 3-4 times a week, you are 'moderately active', not 'very active'.

It depends on how you set up your numbers. If you used an activity multiplier in this calculator (anything above sedentary), your exercise calories are already included in TDEE — do not add them again. If you set sedentary and want to track exercise separately, eat back 50-75% of what your fitness tracker shows, because consumer wearables typically overestimate calorie burn by 10-30%. The simplest approach is to use the activity multiplier, ignore individual workout burn, and let your weekly weight trend tell you if the number is right.

The most common reasons: underestimating intake (cooking oils, drinks, weekend meals out, "bites and tastes" while cooking), overestimating burn, water retention masking fat loss for 1-3 weeks, hormonal shifts, and adaptive thermogenesis (your body running more efficiently after weeks in a deficit). If you have been eating at the target for 3 weeks without weight change, reduce calories by 100-150 kcal/day or add a 20-minute walk daily, and re-evaluate after another 2 weeks.

Most professional health bodies advise not eating below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. Very low calorie diets (VLCDs, under 800 kcal/day) can cause nutrient deficiencies, fatigue, muscle loss, gallstones, hair loss, and severe metabolic adaptation that makes weight maintenance harder long-term. Slow, sustainable deficits of 500 kcal/day or less are nearly always the better choice.

A balanced split that works for most goals is 30% protein, 40% carbohydrate, 30% fat. For fat loss or muscle gain, prioritise protein at 1.6-2.2 g per kg of body weight (or 0.7-1.0 g per lb) and fill the rest with carbs and fat to taste. Athletes performing high-intensity training benefit from higher carbs (40-55%); those doing endurance work or following keto skew higher fat. Use our macro calculator to see the gram counts for different splits.

Yes, but more slowly than most people think. After 20, BMR drops by about 1-2% per decade, largely because lean muscle mass naturally declines with age. The much bigger driver of "middle-age weight gain" is reduced physical activity, not metabolism itself. Maintaining strength training into your 40s, 50s, and beyond preserves muscle and keeps your calorie needs higher. Re-run this calorie calculator every 5 years or after any major weight change.

The Mifflin-St Jeor equation uses height, weight, age, and sex but does not directly account for muscle vs. fat. For most people in a normal body-fat range, this is fine — the formula was validated across thousands of mixed-composition adults. If you are very lean and muscular (or very obese), the Katch-McArdle equation, which uses lean body mass measured by DEXA, BIA, or callipers, will give a more accurate BMR. Most online calculators (including this one) use Mifflin-St Jeor because it doesn't require body-fat percentage input.

This calorie calculator is designed for adults 18 and older. Children, teenagers, pregnant women, and breastfeeding mothers have different calorie and nutrient requirements that go beyond a simple BMR equation. For these groups, please consult a paediatrician, GP, or registered dietitian. Restricting calories below normal growth needs in children and adolescents can affect development and is not recommended without medical guidance.