Caloric Deficit Calculator

Calculate your daily caloric deficit for sustainable weight loss. Free, fast & accurate.

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What is Caloric Deficit Calculator?

This caloric deficit calculator uses the Mifflin-St Jeor equation — the most accurate predictive formula for Basal Metabolic Rate (BMR) — combined with validated activity multipliers to determine your Total Daily Energy Expenditure (TDEE). Adjust the deficit percentage slider to see how different deficit levels affect your daily calorie target, weekly caloric deficit, and projected weight loss. The 12-month chart visualizes your expected weight trajectory, accounting for the mathematical reality that weight loss follows a decreasing curve as your body mass decreases.

Steps:

  1. Select your unit system: metric (kg/cm) or imperial (lbs/inches).
  2. Enter your biological sex, age, weight, and height.
  3. Choose your activity level from sedentary to very active.
  4. Adjust the deficit percentage slider to set your desired caloric deficit (10–40%).
  5. Review your BMR, TDEE, target daily calories, and projected weekly weight loss.
  6. View the 12-month weight projection chart to visualize your journey.

Formula

BMR (Mifflin-St Jeor, men) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. BMR (women) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. TDEE = BMR × activity multiplier (1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 active, 1.9 very active). Target Daily Calories = TDEE × (1 − deficit % ÷ 100). Weekly Caloric Deficit = (TDEE − Target Daily Calories) × 7. Weekly Weight Loss = Weekly Caloric Deficit ÷ 7,700 kcal per kg of body fat.

Use Cases

  • Individuals starting a weight loss journey and needing an evidence-based calorie target
  • Fitness enthusiasts fine-tuning their cut for a specific body composition goal
  • Nutritionists and dietitians calculating client TDEE for meal planning
  • Athletes managing weight class requirements for competition
  • Health-conscious individuals understanding their metabolic baseline

Key Benefits

  • Mifflin-St Jeor BMR — the most accurate predictive formula validated in peer-reviewed research
  • Adjustable deficit slider from 10–40% lets you choose your pace
  • Automatic weight projection over 12 months with realistic diminishing returns
  • Metric and imperial support for global accessibility
  • Visual chart makes your weight loss trajectory tangible and motivating

Pro Tips

  • Recalculate your TDEE every 5–10 lbs (2–5 kg) of weight loss — your calorie needs decrease as you get lighter.
  • Weigh yourself at the same time daily (morning, after bathroom) and use the weekly average to track trends.
  • Eat at least 1.6 g of protein per kg of body weight to preserve muscle mass during a deficit.
  • Never eat below your BMR without medical supervision — it increases the risk of metabolic and hormonal issues.
  • Combine diet and exercise for the most sustainable results — a 300-calorie deficit from food + 200 from exercise is easier than a 500-calorie food deficit alone.
  • If weight loss stalls for 2+ weeks, reduce calories by 100–150 or add 1–2 sessions of moderate exercise rather than making drastic cuts.

Frequently Asked Questions

What is a caloric deficit and how does it cause weight loss?
A caloric deficit occurs when you consume fewer calories than your body burns in a day. Your body must then use stored energy (primarily body fat and some muscle glycogen) to make up the difference. The fundamental principle is thermodynamics: 1 pound of body fat contains approximately 3,500 calories, so a 500-calorie daily deficit theoretically produces about 1 pound of fat loss per week. Real-world results vary due to metabolic adaptation, water retention, and body composition changes.
How do I calculate my TDEE (Total Daily Energy Expenditure)?
TDEE = BMR × Activity Multiplier. First, calculate BMR using the Mifflin-St Jeor equation: Men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. Women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161. Then multiply by your activity factor: 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (active), or 1.9 (very active). Our calculator does this automatically.
What is BMR and why is it different from TDEE?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain vital functions — breathing, circulation, cell production, brain function. It represents roughly 60–70% of your total daily calorie expenditure. TDEE adds your daily activity (exercise, walking, fidgeting, digestion) on top of BMR. Two people with the same BMR can have very different TDEEs if one is a sedentary office worker and the other is a construction worker.
How many calories should I eat to lose weight?
A safe and sustainable deficit is 15–25% below your TDEE. For most people, this means eating 300–750 fewer calories than maintenance per day, resulting in 0.5–1.5 lbs (0.25–0.7 kg) of weight loss per week. Our calculator recommends a default 20% deficit, which balances effective fat loss with metabolic sustainability. Never eat below your BMR without medical supervision.
What is a safe rate of weight loss?
The CDC and most health organizations recommend losing 1–2 lbs (0.5–1 kg) per week. This translates to a 500–1000 calorie daily deficit. Faster weight loss increases the risk of muscle loss, nutritional deficiencies, gallstones, metabolic slowdown, and weight regain. For obese individuals, initial weight loss may be faster due to water weight reduction, but fat loss should still target 1–2 lbs per week.
How does activity level affect my calorie needs?
Activity level can change your TDEE by 40–60%. A sedentary office worker with a BMR of 1,600 calories has a TDEE of approximately 1,920 calories (1,600 × 1.2). The same person who exercises vigorously 6 days per week has a TDEE of approximately 2,760 calories (1,600 × 1.725). This 840-calorie difference means the active person can eat significantly more while still maintaining a deficit.
Should I subtract exercise calories from my deficit?
Exercise calorie estimates are often inaccurate — most machines and wearables overestimate burn by 15–30%. A safer approach is to set your deficit based on your non-exercise activity level and treat exercise calories as a bonus. If you eat at a 500-calorie deficit and burn 300 additional calories through exercise, your actual deficit is 800 — which may be too aggressive. Recalculate TDEE monthly as your weight changes.
Why does weight loss slow down over time?
As you lose weight, your BMR decreases because smaller bodies require fewer calories to function. A person weighing 90 kg has a higher BMR than the same person at 75 kg. This is called 'metabolic adaptation.' Additionally, your body becomes more efficient during exercise, burning fewer calories for the same activity. Recalculate your deficit every 5–10 lbs of weight loss to account for these changes.
What happens if my deficit is too large?
Severe deficits (above 30–35% below TDEE or below BMR) cause: muscle loss (up to 25% of weight lost may be lean mass), metabolic slowdown (BMR drops 10–15% beyond what weight loss alone explains), hormonal disruption (reduced thyroid hormone, increased cortisol, disrupted leptin/ghrelin), nutritional deficiencies, fatigue, irritability, and hair loss. For sustainable fat loss, keep the deficit moderate and prioritize protein intake.
How accurate is the BMR formula used in this calculator?
This calculator uses the Mifflin-St Jeor equation, which is considered the most accurate predictive BMR formula, with accuracy within ±10% of indirect calorimetry measurements. It outperforms the older Harris-Benedict and WHO/FAO equations. However, individual BMRs can vary by 10–15% from the predicted value due to genetics, muscle mass, hormonal factors, and metabolic history. The result is a starting point — adjust based on actual weight trends over 2–3 weeks.
How do I know if I should use metric or imperial units?
Use whichever units you are most comfortable with — the calculator converts internally. Metric users should enter weight in kilograms and height in centimeters. Imperial users should enter weight in pounds and height in inches. The weight loss projection chart will display in your chosen unit system.

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