Calorie Calculator (TDEE)

This calculator estimates your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation, which predicts your Basal Metabolic Rate (BMR) from age, weight, height and sex. BMR is then multiplied by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active) to give total calories burned per day.

To lose weight, you need a calorie deficit — typically 500 kcal per day for a loss of roughly 0.5 kg per week. To gain weight, a surplus of 250–500 kcal per day is recommended. The NHS advises daily reference intakes of 2,000 kcal for women and 2,500 kcal for men, though individual needs vary considerably.

Enter your details and goal, and the calculator will show maintenance calories plus adjusted targets for weight loss or gain. Results are estimates — track your weight over two to three weeks and adjust intake by 100–200 kcal if progress stalls.

How many calories do I need daily? UK government guidance: women 2,000 kcal, men 2,500 kcal — but actual needs vary by age, weight, height, activity. Use Mifflin-St Jeor formula (most accurate for general adults): BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 (men) or −161 (women). Multiply by activity factor: 1.2 sedentary, 1.4 light, 1.55 moderate, 1.725 active, 1.9 very active. A 30-year-old 80kg male, 180cm, moderately active needs ~2,700 kcal/day.

Calorie deficit for weight loss. 500-750 kcal/day deficit produces 0.5-0.75 kg/week weight loss — NHS recommends not exceeding 1 kg/week. NHS minimum 1,500 kcal/day for women, 1,800 for men under sustained low-calorie diets — below these, get medical supervision. Crash diets are typically counterproductive: rebound weight gain in 70%+ of dieters within 2 years. Sustainable 250-500 kcal/day deficit + protein increase + strength training preserves muscle.

Calorie surplus for muscle gain. To gain muscle: 250-500 kcal/day surplus + 1.6-2.2g protein/kg body weight + resistance training 3-5×/week. Larger surpluses just add fat. Realistic muscle gain rate: 0.25-0.5kg per month for beginners; 0.1-0.25kg for intermediate; less for advanced. Multi-year 'lean bulk' alternating 8-12 weeks surplus with 4-6 weeks deficit is optimal for body recomposition.

Calorie counting accuracy and macros. Manufacturer calorie counts can be 8-25% wrong (FDA allows ±20%). Restaurant calories often higher than menu states. Best apps: MyFitnessPal (huge UK database), Cronometer (nutrient detail), Lose It! Track 80% of meals to spot patterns — perfection isn't required. Macros matter: protein 1.6g/kg minimum; fat 0.5g/kg minimum for hormones; remaining calories from carbs. Sleep 7-9 hours/night — sleep deprivation increases hunger hormones (ghrelin) and reduces satiety (leptin).