Calorie Deficit Calculator

What Is a Calorie Deficit?

A calorie deficit exists when you consume fewer calories than your body burns in a day. Your Total Daily Energy Expenditure (TDEE) is the total calories your body uses — including your basal metabolic rate plus all physical activity. When you eat below this number, your body draws on stored energy reserves — primarily body fat — to make up the difference.

The relationship is straightforward: one kilogram of body fat stores approximately 7,700 kcal of energy. A deficit of 500 kcal/day means a weekly deficit of 3,500 kcal, which equates to roughly 0.45 kg of fat loss per week. This is why 0.5 kg per week is the most commonly recommended target — it sits right at the sustainable threshold where fat loss is meaningful but muscle preservation is achievable.

How to Use Your Calorie Deficit Result

Your calculator result gives you three actionable numbers:

• Daily calorie target: Eat this many calories every day — not just on gym days
• Daily deficit: How many calories below your maintenance this represents
• Goal date: When you will reach your goal weight at this rate — assuming consistency

The goal date is a projection, not a guarantee. Week-to-week weight fluctuates due to water retention, glycogen levels, and digestive contents. Track using a 7-day rolling average of daily weigh-ins for the most accurate read on your progress.

Choosing the Right Deficit Size

Not all deficits are equal. A 250 kcal/day deficit is gentle and very sustainable but slow. A 500 kcal/day deficit is the sweet spot recommended by most dietitians — fast enough to see progress, moderate enough to preserve muscle and avoid fatigue. A 750–1,000 kcal/day deficit works faster but increases the risk of muscle loss, nutritional deficiency, and metabolic adaptation (where your body reduces its resting metabolic rate in response to restriction).

For most people targeting fat loss rather than simply weight loss, 500 kcal/day deficit combined with adequate protein (1.6–2.2g/kg bodyweight) and resistance training is the evidence-based gold standard.

Why Your Deficit Will Change Over Time

Here is the most commonly misunderstood aspect of calorie tracking: as you lose weight, your TDEE decreases. A person who weighs 85 kg burns more calories at rest and during activity than the same person after losing 10 kg. If you set a 500 kcal deficit at 85 kg and never recalculate, by the time you reach 78 kg, your actual deficit may have shrunk to only 200–300 kcal — dramatically slowing your progress.

The solution: recalculate your TDEE and deficit every 4–6 weeks using your current weight. This is the single most important habit for sustained weight loss progress beyond the first 2–3 months.

The Role of Protein in a Deficit

During a calorie deficit, your body can break down both fat and muscle for fuel. Keeping protein intake high (1.6–2.2g per kg of bodyweight) is the primary defence against muscle loss — protein requires significantly more energy to digest (high thermic effect), maximally stimulates muscle protein synthesis, and is the most satiating macronutrient, making it easier to stick to your calorie target. Use our Macro Calculator to set your full macronutrient targets including protein.