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Calorie Deficit Calculator

Calculate the calorie deficit needed to reach your goal weight safely. Estimates daily calories, weight loss rate, and realistic timelines.

Sources: WHO — Obesity and overweight fact sheet · Mifflin-St Jeor et al. (1990) — Predictive equation for resting energy expenditure

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How to Calculate Calorie Deficit for Weight Loss

A calorie deficit is the fundamental principle of weight loss: to lose weight you need to consume fewer calories than your body burns. This calculator helps determine the daily deficit needed to reach your goal weight in your desired timeframe, assessing whether the rate is safe and sustainable.

The Calculation

The calculation happens in three steps:

  1. Basal Metabolic Rate (BMR) via the Mifflin-St Jeor formula, multiplied by the activity factor to get TDEE (total daily expenditure).
  2. Total deficit needed: the weight to lose (in kg) is multiplied by 7,700 kcal (energy in 1 kg of fat tissue).
  3. Daily deficit: the total deficit is divided by the number of days in your chosen period. Calories to eat = TDEE - daily deficit (minimum 1,200 kcal).

Safe vs Aggressive Deficit

WHO and health guidelines recommend gradual weight loss of 0.5-1 kg per week. More aggressive deficits carry significant risks: muscle loss, metabolic slowdown, nutritional deficiencies, and higher likelihood of regaining the weight (yo-yo effect).

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Frequently Asked Questions

What is a calorie deficit?▼
A calorie deficit occurs when you consume fewer calories than your body burns daily (TDEE). It is the only mechanism that causes fat loss. To lose 1 kg of fat requires a total deficit of about 7,700 kcal. A 500 kcal/day deficit produces about 0.5 kg loss per week, considered a safe and sustainable rate.
What is the maximum safe calorie deficit?▼
Guidelines recommend not exceeding a 500-750 kcal/day deficit for most people, corresponding to 0.5-0.75 kg/week loss. Deficits above 1000 kcal/day are considered aggressive and increase risk of muscle loss, nutritional deficiencies, and metabolic slowdown. Never go below 1200 kcal/day (women) or 1500 kcal/day (men) without medical supervision.
Why is my weight not dropping despite the deficit?▼
Common causes include: errors in estimating calories consumed (30-50% underestimation is frequent), water retention due to stress or sodium changes, metabolic adaptation after weeks of prolonged restriction, and unconscious compensation of physical activity. If the plateau persists beyond 3-4 weeks, reassess portions or consider a maintenance calorie week (diet break).