Calorie Deficit Calculator
Daily calories to lose weight safely
Enter your details to calculate your daily calorie target for weight loss.
Daily Calorie Target
0
— calorie deficit
Your NumbersCalories
BMR (at rest)—
TDEE (maintenance)—
Daily deficit—
Daily calorie target—
Expected weekly loss—
Minimum safe calories1,200 (F) / 1,500 (M)
Protein target—
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How Calorie Deficit Works
A calorie deficit means consuming fewer calories than your body burns (TDEE). Since 1 lb of fat is approximately 3,500 calories, a 500 calorie/day deficit creates roughly 1 lb/week of fat loss. This is the basis for most weight loss recommendations.
Your TDEE (Total Daily Energy Expenditure) is calculated from your BMR (Basal Metabolic Rate — calories burned at rest) multiplied by an activity factor. This calculator uses the Mifflin-St Jeor equation, considered the most accurate for most people. Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision.
Mifflin-St Jeor Equation
The most validated BMR formula for most adults. Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5. Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. Multiply by activity factor (1.2-1.9) to get TDEE. Accuracy within 10% for 70-80% of people; less accurate for extremes of body composition.
Safe Rate of Loss
Most health authorities recommend losing no more than 0.5-1 kg (1-2 lbs) per week. Faster loss increases lean muscle loss, nutrient deficiencies, and metabolic adaptation. A 500 cal/day deficit (1 lb/week) is the classic evidence-based target. Deficits beyond 1,000 cal/day are generally not recommended without medical supervision.
Protein During Deficit
Higher protein intake (1.6-2.2g per kg of body weight) during a calorie deficit preserves lean muscle mass. Protein also has the highest thermic effect of food (20-30% of calories are used in digestion vs 5-10% for carbs and 0-3% for fat). Prioritising protein at each meal is one of the most effective practical strategies for maintaining muscle while losing fat.
Metabolic Adaptation
As you lose weight, your TDEE decreases because: smaller body requires less energy, metabolic rate adapts (adaptive thermogenesis). This is why weight loss slows over time even at the same deficit. Plan to recalculate TDEE after every 5-10 lbs of weight loss and adjust calories downward or increase activity to maintain the deficit.
Calorie calculations are estimates. Individual metabolism varies. Consult a healthcare professional or registered dietitian before starting any weight loss program, especially if you have medical conditions.
Frequently Asked Questions
What is a calorie deficit?+
A calorie deficit occurs when you consume fewer calories than your body burns in a day. Your body then uses stored fat (and some protein from muscle) to make up the difference. A 500 calorie/day deficit creates a weekly deficit of 3,500 calories, roughly equivalent to 1 lb (0.45 kg) of fat. This is why 1 lb/week is the standard recommended rate of loss.
How many calories should I eat to lose weight?+
Start from your TDEE (Total Daily Energy Expenditure) and subtract your target deficit. This calculator calculates your TDEE using the Mifflin-St Jeor equation and your activity level. A 500 cal/day deficit is recommended for most people aiming for 1 lb/week loss. Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision.
How many calories is a 1 pound deficit?+
The traditional estimate is 3,500 calories = 1 lb of fat. This comes from the energy content of adipose tissue (~7,700 kcal/kg). In practice, weight loss is not perfectly linear because the body also loses water, glycogen, and some muscle — and metabolic rate adapts. The 3,500 calorie rule is a useful approximation; actual results vary by individual.
What is TDEE?+
TDEE (Total Daily Energy Expenditure) is the total calories your body burns in a day, accounting for all activity. It's calculated as BMR x activity factor. BMR is the calories needed at rest to maintain basic functions. Sedentary TDEE: BMR x 1.2. Moderately active: BMR x 1.55. Very active: BMR x 1.725. For most adults, TDEE ranges from 1,600 to 3,000 calories depending on size and activity.
How fast can I safely lose weight?+
Safe rate: 0.5-1 kg (1-2 lbs) per week for most adults. For people with obesity (BMI 35+), 2-2.5 lbs/week may be appropriate under medical supervision. Faster loss: increases muscle loss, micronutrient deficiencies, gallstones, and metabolic adaptation. Very low calorie diets (under 800 kcal) require medical supervision. Studies consistently show slower loss rates result in more sustainable outcomes and better muscle preservation.
What is BMR?+
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to maintain basic functions like breathing, circulation, and organ function. It accounts for 60-70% of total daily calorie burn. The Mifflin-St Jeor equation: Men: (10 x weight_kg) + (6.25 x height_cm) - (5 x age) + 5. Women: (10 x weight_kg) + (6.25 x height_cm) - (5 x age) - 161.
Should I eat back exercise calories?+
This depends on how your TDEE was calculated. If using an activity multiplier (like this calculator), exercise is already partially included. If tracking individual workouts separately, eating back 50-75% of exercise calories is a conservative approach (trackers often overestimate). The simplest approach: choose an accurate activity multiplier and maintain a consistent deficit from that TDEE without separately tracking workout calories.
How do I overcome a weight loss plateau?+
Plateaus occur because: you've lost weight (lower TDEE), metabolic adaptation, or tracking errors accumulate. Solutions: recalculate TDEE and reduce calories by 100-150 kcal, increase activity rather than further reducing food, take a 1-2 week 'diet break' at maintenance calories (research shows this reduces adaptive thermogenesis), recheck food logging accuracy (portion creep is common). Most plateaus are not biological failures but tracking or calculation issues.
Does the type of food matter or just calories?+
For weight loss, calories are the primary driver — but food type matters for satiety, muscle preservation, and adherence. High-protein foods preserve muscle during deficit. High-fiber foods increase satiety per calorie. Ultra-processed foods are engineered to be hyperpalatable and lead to overconsumption. Practical hierarchy: first get calories right, then prioritise protein (1.6-2g/kg), then vegetables and fiber, then overall diet quality.
What is the minimum safe calorie intake?+
NHS and most health authorities recommend: Women: not below 1,200-1,400 kcal/day. Men: not below 1,500-1,800 kcal/day. Very low calorie diets (VLCDs, 400-800 kcal/day) are medically supervised programs for specific conditions. Going below minimums risks: nutrient deficiencies, muscle loss, hair loss, hormonal disruption, gallstones, and disordered eating. If your calculated target is below the minimum, reduce your deficit goal or extend your timeline.