Calorie Deficit Calculator
Enter your TDEE and daily calorie target to see your deficit, projected fat loss rate, and estimated time to goal weight.
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How many calories your body burns per day
How many calories you plan to eat per day
Optional — needed for timeline estimate
Optional — needed for timeline estimate
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Your deficit breakdown will appear here
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A calorie deficit is the fundamental driver of fat loss. No matter which diet or eating pattern you follow — whether that's keto, intermittent fasting, or a standard balanced diet — fat loss happens when you consume fewer calories than your body burns. This calculator helps you find your specific deficit and project how long it will take to reach your goal weight.
What Is a Calorie Deficit?
A calorie deficit occurs when your total daily calorie intake is lower than your Total Daily Energy Expenditure (TDEE). Your TDEE is the number of calories your body burns each day, accounting for your resting metabolism, digestion (the thermic effect of food), and all physical activity.
The widely-cited "3,500 calories per pound" rule states that a cumulative deficit of 3,500 calories results in approximately 1 pound of fat loss. While this is a simplification (actual fat loss varies by individual, hormone status, and composition of weight lost), it's a reliable enough estimate for planning purposes. A more precise conversion: 7,700 kcal ≈ 1 kg of body fat.
How to Calculate Your Calorie Deficit
- Find your TDEE — Use the TDEE Calculator to determine how many calories your body burns daily.
- Choose your deficit size — A 10% deficit is gentle and sustainable. A 20% deficit produces faster results but requires more dietary discipline. Anything above 25% risks significant muscle loss and metabolic slowdown.
- Set your daily calorie target — Subtract your chosen deficit from your TDEE. This is how many calories you should eat per day.
- Project your timeline — Enter your current and goal weight to see how many weeks it will take at your chosen deficit level.
How Fast Will I Lose Weight?
At a 500-calorie daily deficit, you create a weekly deficit of 3,500 calories — approximately 1 lb (0.45 kg) of fat per week. At a 250-calorie deficit, you'd lose about 0.5 lbs per week. The first 1–2 weeks often show faster scale movement due to water weight loss, especially on lower-carbohydrate diets, but this is not the same as fat loss.
| Daily Deficit | Weekly Deficit | Est. Weekly Loss | Pace |
|---|---|---|---|
| 250 kcal | 1,750 kcal | ~0.5 lbs / 0.2 kg | Slow & sustainable |
| 500 kcal | 3,500 kcal | ~1 lb / 0.45 kg | Recommended |
| 750 kcal | 5,250 kcal | ~1.5 lbs / 0.7 kg | Aggressive |
| 1,000 kcal | 7,000 kcal | ~2 lbs / 0.9 kg | Maximum — not for most people |
Common Mistakes That Ruin a Calorie Deficit
- Eating back exercise calories — If you're using an activity multiplier in your TDEE, your exercise is already accounted for. Don't double-count it.
- Liquid calories — Coffee drinks, juices, alcohol, and protein shakes add up fast and are often not tracked carefully.
- Portion underestimation — Studies show people routinely underestimate portion sizes by 20–40%. Weighing food with a kitchen scale is significantly more accurate than eyeballing.
- Not recalculating — As you lose weight, your TDEE decreases. Failing to recalculate every 4–6 weeks means you're chasing an outdated target.
Frequently Asked Questions
A calorie deficit occurs when you consume fewer calories than your body burns in a day. Your TDEE represents the number of calories you burn daily. If your TDEE is 2,500 calories and you eat 2,000 calories, you are in a 500-calorie deficit. Over seven days, that creates a 3,500-calorie deficit — approximately equivalent to 1 pound of body fat
A moderate deficit of 10–20% below your TDEE is recommended for most people. This typically means 300–600 calories per day. Aggressive deficits (greater than 25%) increase the risk of muscle loss, nutrient deficiencies, metabolic adaptation, and fatigue. The safest and most sustainable approach is losing 0.5–1% of your body weight per week
For most adults, 1,200 calories per day is below the BMR and should only be followed under medical supervision. Eating below your BMR long-term causes muscle loss, slows metabolism, and leads to nutrient deficiencies. If your calculated target is below 1,400 calories, consult a registered dietitian before proceeding. Sustainable fat loss rarely requires going below 1,400–1,500 calories.
Several factors can cause a weight loss plateau: metabolic adaptation (your body lowering TDEE in response to sustained restriction), water retention (masking fat loss on the scale), inaccurate calorie tracking, or underestimating food intake. First, verify your tracking accuracy. If accurate, try a 100-calorie reduction, a diet break at maintenance for 1–2 weeks, or increasing daily activity rather than cutting calories further.
At a 500-calorie daily deficit, you can expect to lose approximately 1 pound (0.45 kg) per week. At a 250-calorie deficit, approximately 0.5 pounds per week. Divide your total weight loss goal in pounds by your expected weekly loss rate. Note that early weight loss is often faster due to water weight, and the rate naturally slows as you get closer to your goal