What is a calorie deficit?
A calorie deficit means eating fewer calories than your body burns. Your body covers the gap with stored energy, mostly body fat, and your weight goes down over time.
How the timeline is calculated
The calculator finds your maintenance calories (TDEE), then subtracts enough to lose weight at the pace you pick. A pound of body fat holds about 3,500 kcal, so:
| Pace | Daily deficit | Weekly loss |
|---|---|---|
| Lose slow | about 250 kcal | 0.5 lb |
| Lose | about 500 kcal | 1 lb |
| Lose fast | about 1,000 kcal | 2 lb |
It divides the weight you want to lose by your weekly pace to estimate the number of weeks and your finish date.
Why real progress is slower at times
Weight drops quickly in the first week or two, mostly from water. After that, progress slows. As you get lighter your body burns fewer calories, so recalculate every 10 lb or so. Short plateaus are normal; look at your trend over 3–4 weeks, not day to day.
How to use the calorie deficit calculator
- Fill in "About you" and choose how fast you want to lose weight: 0.5, 1 or 2 lb a week.
- Enter your target weight.
- See the date you could reach it, the number of weeks, and how many calories to eat each day.
Example: losing 20 lb
A 180 lb man with a maintenance of about 2,739 calories wants to reach 160 lb. At 1 lb a week he'd eat about 2,240 calories and reach his goal in about 20 weeks. At 0.5 lb a week he'd eat about 2,490 calories and need about 40 weeks. The slower plan is easier to live with; the faster one gets there sooner. Neither is wrong.
What is a safe calorie deficit?
A deficit of 300–500 calories a day suits most people. The CDC notes that people who lose weight gradually, about 1–2 lb a week, are more likely to keep it off. Most adults shouldn't eat below about 1,200 calories (women) or 1,500 (men) without medical supervision; the calculator warns you if your target drops below these levels.
Tips to reach your date
- Weigh yourself 3–7 times a week and track the weekly average, not single days.
- Keep protein high and lift weights 2–3 times a week to protect muscle.
- Walk more. See how many steps a day to lose weight.
- Recalculate every 10 lb; your deficit shrinks as your weight drops.
Read the complete guide: calorie deficit explained: how to lose weight without starving.
Frequently asked questions
How do I calculate my calorie deficit?
To calculate your calorie deficit, first determine your Total Daily Energy Expenditure (TDEE). Next, subtract your target deficit (typically 500 calories per day to lose 1 pound per week, or 750 calories for faster safe fat loss).
What is the calorie deficit formula?
The calorie deficit formula is: Calorie Deficit = Maintenance Calories (TDEE) - Daily Calorie Intake. If your maintenance level is 2,200 calories and you consume 1,700 calories, your daily deficit is 500 calories.
How big should my calorie deficit be?
A safe, sustainable deficit is between 300 and 750 calories per day (15% to 25% below your maintenance calories). This rate allows for consistent fat loss while preventing severe hunger, metabolic slowdown, and muscle breakdown.
Is losing 2 lb a week safe?
Losing 1 to 2 lb (0.5 to 1 kg) per week is considered safe by health organizations. A 2 lb per week loss requires a 1,000 calorie daily deficit, which is best achieved through a combination of moderate calorie reduction and regular exercise.
Do I need to exercise to lose weight in a deficit?
No, fat loss is primarily driven by nutritional calorie intake. However, combining cardiovascular exercise and resistance training preserves lean muscle, elevates energy expenditure, and improves metabolic health during a cut.
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