# Calorie Deficit Calculator

Calculate your daily calorie deficit for weight loss. Get a personalized calorie target based on your TDEE, goal weight, and timeframe using.

## What this calculates

A calorie deficit occurs when you consume fewer calories than your body burns. This calculator uses the Mifflin-St Jeor equation to estimate your TDEE, then calculates the daily calorie target needed to reach your goal weight in your chosen timeframe.

## Inputs

- **Gender**
- **Current Weight** (kg) — min 30, max 500
- **Goal Weight** (kg) — min 30, max 500
- **Height** (cm) — min 100, max 250
- **Age** (years) — min 15, max 120
- **Timeframe** (weeks) — min 1, max 200
- **Activity Level** — options: Sedentary (little or no exercise), Lightly active (1–3 days/week), Moderately active (3–5 days/week), Very active (6–7 days/week), Extra active (very hard exercise/physical job)

## Outputs

- **Estimated TDEE** — Your estimated Total Daily Energy Expenditure
- **Daily Calorie Target** — Calories to eat per day to reach your goal
- **Daily Deficit** — Caloric deficit per day
- **Weekly Deficit** — Total weekly caloric deficit

## Details

Weight loss fundamentally requires a calorie deficit — consuming fewer calories than your body expends. One kilogram of body fat stores approximately 7,700 calories, so losing 0.5 kg per week requires a daily deficit of about 550 calories. This calculator first estimates your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation, then multiplies by your activity level to determine your Total Daily Energy Expenditure (TDEE). The deficit is calculated based on the total weight you want to lose and your desired timeframe.

For safe, sustainable weight loss, most health professionals recommend losing no more than 0.5–1 kg (1–2 lbs) per week. Extreme deficits can lead to muscle loss, nutritional deficiencies, metabolic adaptation, and other health issues. This calculator enforces a minimum daily intake of 1,500 calories for men and 1,200 for women. Always consult a healthcare professional or registered dietitian before beginning a weight loss plan.

## Frequently Asked Questions

**Q: How large should my calorie deficit be?**

A: A moderate deficit of 500–750 calories per day is generally recommended, leading to about 0.5–0.75 kg of weight loss per week. Deficits larger than 1,000 calories per day increase the risk of muscle loss and metabolic slowdown and should only be done under medical supervision.

**Q: Is it safe to eat below my BMR?**

A: Eating below your BMR for extended periods is generally not recommended. Your BMR represents the minimum energy your body needs for basic functions like breathing and circulation. Sustained under-eating can slow your metabolism, cause nutrient deficiencies, and lead to muscle loss.

**Q: Why is my weight loss slowing down?**

A: As you lose weight, your BMR and TDEE decrease because your body requires less energy to maintain a smaller mass. This is called metabolic adaptation. You may need to recalculate your deficit periodically or increase physical activity to maintain the same rate of weight loss.

**Q: Should I eat back exercise calories?**

A: It depends on your deficit size. If your deficit is already moderate (500 calories), eating back some exercise calories can prevent the total deficit from becoming too large. However, calorie burn estimates from exercise are often overstated, so eating back 50–75% of estimated exercise calories is a common recommendation.

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Source: https://vastcalc.com/calculators/health/calorie-deficit
Category: Health & Fitness
Last updated: 2026-04-21