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 big should my calorie deficit be?
A deficit of 300–500 kcal a day suits most people. Larger deficits work faster but are harder to keep up and can cost muscle.
Is losing 2 lb a week safe?
For people with a lot of weight to lose, 2 lb a week can be fine for a while. Most people do better at 0.5–1 lb a week. Talk to a doctor before a very aggressive plan.
Why am I not losing weight in a deficit?
The most common reasons are underestimating portions, water retention, or a calorie target that is too high. Track carefully for two weeks, then lower your intake by 100–200 kcal if needed.
Do I need to exercise to lose weight?
You can lose weight with diet alone, but exercise, especially strength training, helps keep muscle and makes it easier to keep the weight off.
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