Daily Calorie Deficit Calculator
Find exactly how many calories you need to cut each day to reach your target weight by a set deadline. Use this when planning a structured weight-loss diet with a specific goal and timeframe.
About this calculator
To lose body fat, you must consume fewer calories than you burn. The formula used here is: Daily Deficit = ((currentWeight − targetWeight) × 7700) / (timeframe × 7). The constant 7700 represents the approximate number of calories stored in one kilogram of body fat. Multiplying the total weight to lose by 7700 gives the total calorie deficit needed. Dividing by the total number of days (weeks × 7) spreads that deficit evenly across the timeframe. For example, losing 5 kg in 10 weeks requires a total deficit of 38,500 calories, or 550 calories per day. Keeping the daily deficit between 300–750 calories is generally considered safe and sustainable by nutrition guidelines.
How to use
Suppose you currently weigh 85 kg and want to reach 80 kg in 8 weeks. Step 1: Calculate weight to lose — 85 − 80 = 5 kg. Step 2: Multiply by 7700 — 5 × 7700 = 38,500 total calories. Step 3: Divide by total days — 8 weeks × 7 = 56 days. Step 4: Daily deficit = 38,500 ÷ 56 ≈ 688 calories per day. This means you need to eat roughly 688 fewer calories than you burn each day to hit your goal on schedule.
Frequently asked questions
How many calories per day should I cut to lose 1 kg per week?
Losing 1 kg per week requires a daily calorie deficit of approximately 1,100 calories, since 1 kg of fat contains about 7,700 calories. Most health professionals consider this an aggressive target and recommend no more than 0.5–1 kg of loss per week for safety. Combining a moderate dietary reduction with regular exercise makes this more achievable. Always consult a healthcare provider before pursuing large daily deficits.
Why does the calculator use 7700 calories per kilogram of fat?
One kilogram of human body fat tissue contains roughly 7,700 kilocalories of stored energy, which is the widely accepted figure used in nutritional science. This differs slightly from the pure fat energy density of about 9,000 kcal/kg because body fat tissue is not 100% lipid — it also contains water and protein. The 7,700 figure is a practical average used in clinical and dietary settings. It provides a reliable estimate for planning weight-loss timelines, even if individual metabolism varies.
Is a daily calorie deficit of 500 calories safe for weight loss?
A 500-calorie daily deficit is generally considered safe for most healthy adults and is a common recommendation from dietitians. It produces a loss of roughly 0.45 kg (1 lb) per week, which falls within the 0.5–1 kg per week range deemed sustainable. Deficits larger than 1,000 calories per day can risk muscle loss, nutrient deficiencies, and metabolic slowdown. Pairing the deficit with adequate protein intake and resistance exercise helps preserve lean muscle mass during weight loss.