Calorie Deficit Calculator
See your daily calories and weekly fat loss for any deficit.
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A calorie deficit means eating fewer calories than your body burns, which forces it to draw on stored fat for the missing energy. It is the one condition every diet for fat loss has in common, whatever else they call it. This calculator works out your daily calorie target by taking your Total Daily Energy Expenditure (TDEE) and subtracting the deficit you choose, then shows how quickly that deficit turns into weight loss each week and month.
How the deficit becomes fat loss
One kilogram of body fat stores roughly 7,700 calories. To lose it you have to accumulate a 7,700 calorie shortfall, so your weekly rate of loss is simply your daily deficit times seven, divided by 7,700. A 500 calorie daily deficit comes to 3,500 calories a week, which works out to about 0.45 kg of fat lost per week. A larger 1,100 calorie deficit reaches 7,700 over seven days and loses close to 1 kg a week.
Your daily target is your maintenance calories minus the deficit. If your TDEE is 2,760 calories and you take a 500 calorie deficit, you eat 2,260 calories a day. The calculator estimates TDEE from your sex, age, height, weight and activity using the Mifflin-St Jeor equation, so all you have to choose is how big a gap to run.
How big should your deficit be?
A deficit of 300 to 750 calories a day suits most people and produces about 0.3 to 0.7 kg of fat loss a week, slow enough to protect muscle and easy enough to stick to. Bigger cuts lose weight faster on paper but cost energy, training quality and adherence, and more of the loss comes from muscle rather than fat. Keep your intake at or above roughly 1,200 calories a day and eat plenty of protein to hold on to lean mass while you lose.
Aggressive crash diets also tend to backfire because hunger and fatigue lead to skipped workouts and rebound eating. For most people a moderate, sustainable deficit they can maintain for months beats a steep one they abandon in a week.
Why progress slows down
Weight loss is rarely linear. As you get lighter your TDEE falls, because a smaller body burns fewer calories at rest and in motion, so the deficit that once lost half a kilo a week gradually shrinks toward zero. Day to day the scale also swings with water, salt and food in your gut, which can hide real fat loss for a week or more. Recalculate your numbers after every three to five kilograms, judge progress over two to three week averages rather than single days, and trim another 100 to 200 calories if the trend genuinely stalls.
How to use
- 01
Find your TDEE
Enter your stats and activity level so we can estimate maintenance calories.
- 02
Choose a deficit
Pick how aggressive to be — a moderate deficit is easiest to sustain.
- 03
See your plan
Read your daily calorie target and projected weekly and monthly fat loss.
Frequently Asked Questions
A deficit of 300–750 kcal per day is sustainable for most people, giving roughly 0.3–0.7 kg of fat loss per week.
About 7,700 kcal. A daily 1,100 kcal deficit therefore loses roughly 1 kg per week.
Yes. Very large deficits cost muscle, energy and adherence. Keep at least 1,200 kcal per day and prioritise protein.
As you lose weight your TDEE drops, so recalculate every few kilograms and adjust your intake.
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Last reviewed June 2026 · Methodology & sources