How big should your calorie deficit be?
For most people: 15–25% below maintenance, which works out to roughly 300–700 kcal a day.
Expressed as results, that is about 0.5 to 1.5 lb (0.25–0.7 kg) a week. The honest version of this answer is that the right size is the largest one you can hold for as long as the goal takes — and that is usually smaller than the one you first pick.
The table
| Deficit | Weekly loss | Verdict |
|---|---|---|
| 250 kcal | ~0.5 lb | Very sustainable, slow |
| 500 kcal | ~1 lb | The standard recommendation |
| 750 kcal | ~1.5 lb | Workable for a defined stretch |
| 1,000 kcal | ~2 lb | Rarely held for long |
Is a 1,000 calorie deficit too much?
Usually, yes — though it depends on what it leaves you eating.
For someone with a maintenance of 3,000 kcal, a 1,000 kcal deficit means eating 2,000. That is a lot of food and entirely workable. For someone whose maintenance is 1,800, the same deficit leaves 800 kcal, which is not a diet so much as a medically supervised intervention.
Percentage matters more than the absolute number. A deficit above about 25% of maintenance starts costing you disproportionately:
- More of the loss comes from lean tissue
- Training quality falls, which costs you the muscle-protecting stimulus
- Hunger and preoccupation with food rise sharply
- Incidental movement drops, quietly shrinking the deficit you worked for
That last one is genuinely perverse: cut too hard and your body reduces the spontaneous movement that was contributing to the burn, so a larger deficit on paper produces a smaller one in practice.
Signs it is too large
The mechanisms above are invisible. What you can actually observe is a shortlist, and any two of these together mean the deficit has overshot rather than that you need more discipline:
- Hunger that crowds out everything else, rather than passing
- Feeling cold, flat, or unusually irritable
- Sleep getting worse instead of better
- Strength dropping session after session
- Weekly loss running above about 1% of bodyweight for several weeks
- Hair shedding, or a disrupted menstrual cycle
The last one is a reason to see a doctor, not to shave 100 kcal off. The others are a reason to move back toward 20% and stay there.
The floor
As a general guide, intake below 1,500 kcal for men or 1,200 kcal for women is hard to make nutritionally adequate and is not something to do on your own initiative. If your arithmetic lands under those figures, the answer is a gentler pace or a longer timeline — not a smaller plate.
Our deficit calculator will tell you when your chosen pace crosses that line rather than simply printing the number.
Choosing yours
How you create the gap is up to you — a “calorie deficit diet” is not a particular diet, just any way of eating that gets you there.
Pick 20% of maintenance as a default. It is aggressive enough to see movement within a month and gentle enough to survive a bad week.
Go smaller if you have under 10 lb to lose, you train seriously, you are already lean, or you have a history of rebounding from restriction. The last 10 lb genuinely do come slower, and forcing them costs more than waiting.
Go larger if you have a lot to lose and a high maintenance — someone at 3,200 kcal maintenance can run 800 under and still eat substantially. Even then, plan a return to maintenance every couple of months.
It is not a fixed number
Whatever you choose today describes today. Lose 10 lb and your maintenance falls by roughly 50–100 kcal a day, so an unchanged intake is a shrinking deficit. This is the ordinary reason progress slows around month three, and it is also the reason the answer to “how big should my deficit be” has to be recalculated rather than decided once.
Recheck every 10 lb (4.5 kg) or so.
A long deficit also does not have to run unbroken. One or two weeks back at maintenance pauses progress without undoing it, and it costs about what you would expect — a week off a 500 kcal deficit is roughly 1 lb (0.45 kg) of delayed loss. Most people who abandon a diet do so because it had no exit ramp, which makes a planned pause cheaper than the alternative. More on making one stick.
More on what to do when it stops working, and on running a deficit generally.
General information, not medical advice. Very low calorie intakes should only be undertaken with medical supervision.