Calorie Deficit
Free Calorie Deficit Calculator using the Mifflin-St Jeor formula. Calculate BMR, TDEE, daily deficit intake, weekly weight loss, and time to reach your goal. Supports metric and imperial units.
About This Calculator
A calorie deficit occurs when you consume fewer calories than your body burns, forcing it to use stored fat for energy. This calorie deficit calculator helps you determine your exact daily calorie needs using the Mifflin-St Jeor formula and provides a personalized weight loss projection based on your chosen deficit.
Your Basal Metabolic Rate (BMR) represents the calories your body needs at complete rest — about 60-75% of your total daily burn. By applying an activity level multiplier, we calculate your Total Daily Energy Expenditure (TDEE), also known as your maintenance calories. Subtract your chosen deficit to get your daily calorie intake target. Since 1 kg of body fat equals approximately 7,700 calories, a daily deficit of 500 kcal leads to about 0.5 kg of weight loss per week.
The Mifflin-St Jeor Formula:
- For Males: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
- For Females: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161
Activity Level Multipliers:
- Sedentary (1.2): Little or no exercise
- Light (1.375): Light exercise 1-3 days/week
- Moderate (1.55): Moderate exercise 3-5 days/week
- Active (1.725): Hard exercise 6-7 days/week
- Very Active (1.9): Intense exercise daily or twice/day
Regional Notes:
- India (ICMR): Typical deficits of 300-400 kcal/day, emphasis on reducing refined carbs and increasing protein intake.
- US (Dietary Guidelines): Standard 500 kcal/day deficit for 0.5 kg weekly loss; focus on portion control and reducing added sugars.
- UK (NHS): 500-600 kcal/day deficit recommended for sustainable 0.5-1 kg weekly loss; balanced diet with plenty of fruits and vegetables.
Features:
- Mifflin-St Jeor BMR and TDEE calculation
- Four deficit levels: 250, 500, 750, and 1000 kcal/day
- Weekly and monthly weight loss projections
- Time to lose 5 kg and 10 kg estimates
- Metric and imperial unit support
- Comparison and energy breakdown charts
- Shareable calculation links
- Safe calorie minimum: 1,200 kcal/day floor
Frequently Asked Questions
What is a calorie deficit?
A calorie deficit occurs when you consume fewer calories than your body burns. This forces your body to use stored fat for energy, leading to weight loss. To lose 1 kg of body fat, you need a calorie deficit of approximately 7,700 calories. A daily deficit of 300 to 500 calories is recommended for healthy, sustainable weight loss.
How much of a calorie deficit do I need to lose weight?
For healthy weight loss of 0.5 to 1 kg per week, aim for a daily calorie deficit of 300 to 500 calories. A 500 kcal deficit typically leads to about 0.5 kg weight loss per week. Deficits larger than 1000 kcal per day are not recommended as they may cause muscle loss, nutritional deficiencies, and metabolic slowdown. Always consult a healthcare professional before starting any weight loss plan.
How is BMR used in calorie deficit calculation?
BMR (Basal Metabolic Rate) is the calories your body needs at complete rest. Our calculator uses the Mifflin-St Jeor formula: For males: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5. For females: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161. Your BMR is multiplied by an activity factor (1.2 to 1.9) to get your TDEE (Total Daily Energy Expenditure), which is your maintenance calorie level. The deficit is subtracted from TDEE.
What is the minimum safe calorie intake per day?
Most health authorities recommend a minimum of 1,200 calories per day for women and 1,500 calories per day for men, though individual needs vary. Eating below these levels can lead to nutritional deficiencies, muscle loss, fatigue, and metabolic slowdown. Our calculator automatically caps your deficit intake at 1,200 kcal minimum for safety.
How long does it take to lose weight with a calorie deficit?
With a 500 kcal daily deficit, you can expect to lose about 0.5 kg per week. This means losing 5 kg would take approximately 10 weeks, and 10 kg would take about 20 weeks. Results vary based on individual factors like starting weight, body composition, age, gender, and activity level. Sustainable weight loss is typically 0.5 to 1 kg per week.
Can I exercise to create a bigger calorie deficit?
Yes, combining diet and exercise is the most effective approach for weight loss. Exercise increases your TDEE, allowing for a larger deficit without reducing food intake too much. For example, 30 minutes of running can burn 300-400 calories, effectively adding to your deficit. A combination of diet (300-500 kcal deficit) and exercise (200-300 kcal burn) is often recommended for sustainable results.
What is the difference between calorie deficit in India, US, and UK?
The science of calorie deficit is universal — 1 kg of fat equals approximately 7,700 kcal everywhere. However, dietary recommendations vary: In India (ICMR guidelines), typical diets are already lower in calories, so deficits of 300-400 kcal are recommended. In the US (Dietary Guidelines for Americans), 500 kcal deficit is standard. In the UK (NHS guidelines), a 500-600 kcal deficit is recommended for 0.5-1 kg weekly loss. Portion sizes and food density differ across regions, so choose a deficit that matches your local diet pattern.
Can I build muscle while in a calorie deficit?
Yes, it is possible to build muscle while in a calorie deficit, especially for beginners or those returning after a break. This requires a high-protein diet (1.6-2.2 g per kg of body weight), resistance training 3-4 times per week, and a modest deficit of no more than 300-500 kcal. However, muscle gain will be slower compared to being in a calorie surplus (bulking).