A calorie deficit means eating fewer calories than your body burns in a day. If your body uses 2,000 calories and you eat 1,500, the 500-calorie gap is your deficit, and your body covers it from stored energy — mostly body fat. That gap is the entire mechanism of weight loss: no deficit, no fat loss, whatever diet you follow.
The idea is simple, but the practice is not. How big should the deficit be? How fast should the weight come off? And why does the scale stop moving after a few weeks even when you change nothing? This guide answers all three, with worked numbers.
How Big Should a Calorie Deficit Be?
For most adults, a deficit of 300 to 500 calories a day is the sweet spot: big enough to see progress, small enough to sustain. A 500-calorie daily deficit adds up to 3,500 calories over a week, which the standard rule equates to about 1 pound (0.45 kg) of fat. A 250-calorie deficit gives about half a pound a week; a 750-calorie deficit gives about 1.5 pounds; 1,000 a day gives about 2 pounds.
| Daily deficit | Weekly deficit | Expected loss |
|---|---|---|
| 250 calories | 1,750 calories | About 0.5 lb (0.2 kg) a week |
| 500 calories | 3,500 calories | About 1 lb (0.45 kg) a week |
| 750 calories | 5,250 calories | About 1.5 lb (0.7 kg) a week |
| 1,000 calories | 7,000 calories | About 2 lb (0.9 kg) a week |
A percentage-based deficit scales better than a flat number. A 500-calorie cut is a modest 15 percent trim for someone maintaining on 3,200 calories, but a harsh 30 percent cut for someone maintaining on 1,650. As a rule, aim for 10 to 20 percent below maintenance. On a maintenance of 2,000 calories, that is a deficit of 200 to 400 a day; on 2,500, it is 250 to 500. To find the right size for your body, work out your own calories to lose weight rather than copying someone else’s number.
The CDC describes 1 to 2 pounds a week as a safe, sustainable pace for most adults. Faster than that, and the share of muscle in what you lose rises, hunger becomes harder to manage, and the diet usually ends early.
How Do You Calculate Your Own Deficit?
Three steps, all arithmetic. First, find your maintenance calories (TDEE) — your basal metabolic rate from the Mifflin-St Jeor equation, multiplied by an activity factor from 1.2 (sedentary) to 1.9 (extremely active). Our guide to how to calculate TDEE works through this step by step. Second, choose your deficit: 500 a day is the standard starting point. Third, subtract: maintenance minus deficit is your daily target.
Worked example: a 40-year-old woman, 80 kg, 165 cm, lightly active. BMR = (10 × 80) + (6.25 × 165) − (5 × 40) − 161 = 800 + 1,031.25 − 200 − 161 = 1,470.25. Maintenance = 1,470.25 × 1.375 = 2,021.6, rounded to 2,022. Her target at a 500-calorie deficit is 2,022 − 500 = 1,522 calories a day; at a gentler 300-calorie deficit it would be 1,722. A free calorie calculator runs the same calculation for your own numbers.
Never let the target fall below the floor: about 1,200 calories a day for women and 1,500 for men without medical supervision. Below that, meeting basic protein, vitamin, and mineral needs becomes genuinely difficult. If your maintenance is low — say 1,600 — a 500-calorie deficit would put you at 1,100, below the floor. Take a 250-calorie deficit instead (target 1,350) and add a daily walk to widen the gap.
How Fast Will You Lose Weight?
The 3,500-calorie rule says a pound of body fat stores about 3,500 calories, so a 500-calorie daily deficit should cost a pound a week. In practice, weight loss runs slower than the rule predicts, and the gap grows over time. The rule draws a straight line through a curved reality.
Three things bend the curve. First, your body gets smaller, so it burns less: the woman above, at 70 kg instead of 80 kg, has a maintenance of 1,884 — 138 fewer calories a day — so her 500-calorie deficit has quietly shrunk to 362 if she keeps eating 1,522. Second, the body adapts, burning a little less than predicted, a process called adaptive thermogenesis. Third, people move less without noticing — fewer steps, less fidgeting — which trims daily burn further.
The honest expectation: a 500-calorie deficit produces roughly 0.5 to 1 pound a week at first, tapering over months. That is still real progress — 1 pound a week is 26 pounds in six months. Our guide to how many calories you should eat to lose weight shows how to set the target for your own numbers.
Why Do Weight Loss Plateaus Happen?
A plateau is three to four weeks with no meaningful change in weight despite sticking to the plan. Reviews suggest around 85 percent of people who diet hit one. It is not a sign of failure — it is a sign that the plan needs updating.
Your maintenance fell as you lost weight. This is the most common cause, and the worked example above shows it: 10 kg lost cut 138 calories a day from maintenance. The deficit that worked in month one is smaller in month four. Fix: recalculate your TDEE with your current weight and set a new target.
Uncounted food closed the gap. Studies repeatedly find people under-report what they eat by 20 to 45 percent. Cooking oil, dressings, sauces, drinks, and handfuls of snacks are the usual leaks. One tablespoon of olive oil is about 120 calories; two uncounted tablespoons a day erase almost half of a 500-calorie deficit. Fix: weigh food and track everything for two weeks.
The weekend erased the week. A 500-calorie deficit Monday to Friday saves 2,500 calories. A single weekend day 1,500 calories over maintenance wipes out 1,500 of it, leaving a weekly deficit of only 1,000 — about 0.29 pounds (1,000 ÷ 3,500) instead of the expected 1 pound. Fix: track weekends with the same discipline as weekdays.
Water is hiding the fat loss. Higher-salt meals, new exercise, stress, and hormonal cycles all hold water, and a kilogram or two of water can mask weeks of fat loss on the scale. Fix: judge by weekly averages over three to four weeks, not single weigh-ins, and use waist measurements too.
You move less than you did. Dieting quietly reduces NEAT — the calories of everyday movement — mostly from less fidgeting and sitting more. Fix: set a daily step goal, such as 8,000 to 10,000 steps, and protect it.
You overestimate exercise burn. Fitness trackers commonly overestimate workout calories by 25 to 40 percent. Eating back those estimated calories can erase the deficit entirely. Fix: never eat back tracker calories; treat exercise as a bonus, not a budget.
How to Break a Plateau: A Step-by-Step Fix
Work through this list in order, one step at a time, giving each change two to three weeks before judging it.
- Recalculate your TDEE with your current weight. Use the Mifflin-St Jeor equation and your real activity level. This alone restores the deficit for most people.
- Audit your tracking for two weeks. Weigh food, count oils and dressings, log drinks and snacks. Most plateaus turn out to be tracking gaps, not metabolic damage.
- Hold steady before cutting further. If the stall is only one or two weeks, it may be water. Hold calories steady for two to three weeks and watch the weekly average.
- Add movement, not just less food. Add 2,000 steps a day — roughly 80 to 100 extra calories — or two weekly strength sessions, which protect muscle and keep BMR higher.
- Check protein and sleep. Aim for about 1.6 grams of protein per kilogram of body weight a day (for our 70 kg woman, about 112 grams), and 7 to 9 hours of sleep.
- Only then, trim 100 to 200 calories. Cutting further before fixing tracking or movement just makes the diet harder without fixing the cause. And never cut below the 1,200 / 1,500 floor without medical supervision.
When Is a Deficit Too Big?
A deficit above 1,000 calories a day is the upper limit for most people, and it is rarely necessary. Signs you have gone too far: constant hunger, fatigue, poor sleep, feeling cold all the time, or strength dropping in the gym. These are signals to eat more, not less. Very low intakes also cost muscle, which lowers your BMR and makes future loss harder.
The sustainable deficit is the one you can hold for months. A 500-calorie deficit you keep for six months beats a 1,000-calorie deficit you abandon in three weeks. If you want the other half of the health picture alongside your deficit, your body mass index uses the same weight and height: check it with our free BMI calculator.
FAQ: Calorie Deficit
What is a calorie deficit?
A calorie deficit is eating fewer calories than your body burns in a day. If your body uses 2,000 calories and you eat 1,500, the 500-calorie gap is your deficit, and your body covers it from stored energy, mostly body fat.
How big should my calorie deficit be?
For most adults, 300 to 500 calories a day, or 10 to 20 percent below maintenance. A 500-calorie daily deficit predicts about 1 pound a week at first. Larger deficits are harder to sustain and cost more muscle.
Is a 500 calorie deficit enough to lose weight?
Yes, for most people. It predicts roughly 1 pound (0.45 kg) a week early on. Real loss is usually a little slower, around 0.5 to 1 pound a week, because maintenance falls as you get lighter. If you have not worked out your own number yet, find how many calories you should eat with your age, weight, height, and activity level.
Why am I not losing weight in a calorie deficit?
The most common reasons are a maintenance level that fell as you lost weight, uncounted food, weekend overeating erasing weekday deficits, water retention hiding fat loss, and moving less without noticing. Recalculate your TDEE and track everything for two weeks.
How long does a weight loss plateau last?
A true plateau is three to four weeks with no change. Shorter stalls of one to two weeks are usually water weight. If nothing has moved after four weeks at a recalculated target with honest tracking, trim 100 to 200 calories or add 2,000 daily steps.
Can you lose weight without a calorie deficit?
No. Fat loss requires a sustained net energy deficit — the body must use more energy than it takes in. Diets differ in how they create the deficit, but every diet that works creates one.