Weight Loss Calculator
Calculate your daily calorie target and estimated timeline to reach your goal weight. Based on TDEE, safe deficit guidelines, and evidence-based rate recommendations. Free.
All calculations run instantly in your browser. No data is sent to any server.
Disclaimer: Results are for informational purposes only and do not constitute medical advice, diagnosis, or treatment. Consult a qualified healthcare professional for personal guidance.
How the Calculation Works
This calculator uses the Mifflin-St Jeor equation (Mifflin et al., 1990) to estimate your Basal Metabolic Rate (BMR) — the calories needed at complete rest — then multiplies by your activity factor to get Total Daily Energy Expenditure (TDEE). Your daily calorie target is TDEE minus the deficit required to hit your chosen weekly loss rate. One kilogram of body fat contains approximately 7,700 kcal; losing 0.5 kg/week requires a 550 kcal/day deficit.
Minimum Safe Intake
Calorie targets below 1,200 kcal/day for women and 1,500 kcal/day for men are not recommended without medical supervision. At very low intakes, lean muscle mass is lost alongside fat, and nutritional deficiencies become likely. If the calculator produces targets below these levels, a less aggressive loss rate or medical supervision is indicated.
FAQs
How much deficit to lose weight?
500 kcal/day deficit ≈ 0.5 kg/week loss. Sustainable range: 500–750 kcal/day. Above 1,000 kcal/day deficit increases muscle loss risk.
What is a realistic rate?
NHS and ACSM recommend 0.5–1 kg/week. Faster than 1% of body weight/week risks muscle loss and nutrient deficiency.