Calculate your optimal daily calorie deficit for safe and effective weight loss. Get personalized calorie targets, projected weight loss timelines, and weekly forecasts based on your TDEE and goals. Pure client-side.
A calorie deficit is the foundation of weight loss — it means consuming fewer calories than your body burns. This calculator uses the scientifically validated Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). It then calculates a personalized daily calorie target based on your chosen deficit level and projects how long it will take to reach your goal weight safely. All calculations happen in your browser — no data is sent to any server.
A calorie deficit occurs when you consume fewer calories than your body burns for energy. This forces your body to use stored fat as fuel, resulting in weight loss. It is the scientifically proven foundation of all weight loss — without a deficit, your body has no reason to burn fat reserves.
This calculator uses the Mifflin-St Jeor equation, a scientifically validated formula, to estimate your Basal Metabolic Rate (BMR) — the calories your body burns at rest. It then multiplies BMR by an activity factor to calculate your Total Daily Energy Expenditure (TDEE). Your daily calorie target is TDEE minus your chosen deficit.
BMR (Basal Metabolic Rate) is the number of calories your body needs to maintain basic functions like breathing, circulation, and cell repair while at complete rest. TDEE (Total Daily Energy Expenditure) is your total daily calorie burn including BMR plus calories burned through physical activity, digestion, and daily movement.
Conservative (~0.25 kg/week) is best for long-term sustainability and muscle preservation. Moderate (~0.5 kg/week) is the most popular choice for steady, noticeable results. Aggressive (~1 kg/week) is only recommended for short-term use under professional supervision, as it may lead to muscle loss and nutrient deficiencies.
A moderate calorie deficit is safe for most healthy adults. However, pregnant or breastfeeding women, individuals with eating disorders, teenagers, and people with certain medical conditions should not reduce calories without medical supervision. Always consult a healthcare provider before starting any weight loss plan.
Weight loss plateaus can occur due to water retention, muscle gain, metabolic adaptation, or underestimating calorie intake. Hormonal changes, sleep quality, and stress also affect weight. Ensure accurate tracking, consider a body composition measurement, and allow 2-4 weeks for meaningful trends to emerge.
Beginners and those returning to exercise can build some muscle while losing fat (body recomposition). However, experienced lifters typically need a slight calorie surplus for optimal muscle growth. A conservative deficit combined with resistance training and adequate protein intake maximizes muscle preservation.
Weigh yourself at the same time each day (preferably morning after using the bathroom) and track the weekly average. Take progress photos and body measurements monthly. Use a food tracking app to log meals. Adjust your deficit if weight loss stalls for more than 2-3 weeks.