To lose weight, most adults should eat about 250–750 calories per day below their maintenance level — for many people that lands somewhere near 1,500–2,200 kcal a day, depending on body size, sex, and activity. But there is no single right number: you find yours by estimating your maintenance calories, then subtracting a deficit that produces a safe, steady loss of roughly 0.5–1 kg (1–2 lb) per week. Here is how to work that out for yourself.
Step 1: Find your maintenance calories (TDEE)
Your maintenance level is the number of calories that keeps your weight stable. It is called your Total Daily Energy Expenditure (TDEE), and it is built from two parts:
- Basal metabolic rate (BMR) — the energy your body burns at rest to run your heart, brain, lungs, and other organs. For most people this is the largest slice of the daily total.
- Activity — everything on top of rest: walking, exercise, fidgeting, and the energy it takes to digest food.
The usual method is TDEE = BMR × an activity factor, where the factor runs from about 1.2 (desk job, little exercise) to roughly 1.9 (physical job or twice-daily training). BMR is most commonly estimated with the Mifflin-St Jeor equation, which lands within 10% of measured resting metabolism for around 80% of adults — better than the older Harris-Benedict formula. Work out your resting burn with our BMR calculator, then estimate your maintenance calories with the TDEE calculator.
Every formula is an estimate, not a measurement. Two people of the same height and weight can differ by a few hundred calories a day because of body composition, genetics, and how much they move without noticing. Treat the number as an informed starting point and let the scale correct it over the next few weeks.
Step 2: Understand what a calorie deficit is
A deficit means eating fewer calories than you burn. When incoming energy falls short, your body covers the gap from stored energy — largely body fat — and you lose weight. Eat above maintenance and you are in a surplus (weight gain); eat at maintenance and weight holds.
Body fat stores a lot of energy. As a rule of thumb, one pound of fat holds roughly 3,500 kcal and one kilogram about 7,700 kcal. From that comes the familiar guideline: a deficit of about 500 kcal per day adds up to roughly 3,500 kcal a week, or about 1 lb (0.45 kg) of fat. Both the CDC and NHS point to a 500–1,000 kcal daily deficit to reach a healthy rate of loss.
In practice the "3,500 kcal = 1 lb" model is a simplification. Early weight loss includes water and glycogen, and as you get lighter your maintenance calories fall, so the same deficit yields slightly less over time. It is still a solid planning tool — just expect the scale to behave less mechanically than the arithmetic implies.
Step 3: Pick a safe deficit
Bigger deficit, faster loss — but faster is not always better. Both the NHS and CDC put the safe, sustainable range at 0.5–1 kg (about 1–2 lb) per week. Staying in that band preserves more muscle, feels less punishing, and is far easier to keep up than a crash diet, which is exactly why people who lose weight gradually are more likely to keep it off.
A practical way to choose:
- –250 kcal/day — a gentle deficit (~0.25 kg / 0.5 lb per week). Good if you have less to lose, want to protect training, or prefer a barely noticeable change.
- –500 kcal/day — the classic middle option (~0.45 kg / 1 lb per week). A solid default for most people.
- –750 kcal/day — a firmer deficit (~0.7 kg / 1.5 lb per week). Reasonable if you have more to lose, but harder to sustain and more taxing on energy and recovery.
Two guardrails. First, do not eat below your BMR for long stretches. That is the energy your organs need just to keep you alive; chronically under-eating it leaves no room for daily activity, is hard to maintain, and tends to worsen fatigue, mood, and adherence. If a target pushes you under BMR, shrink the deficit or add activity instead. Second, the NHS advises against dropping below roughly 1,200 kcal/day for women or 1,500 kcal/day for men without clinical supervision — so if a large deficit takes you under those floors, ease off. If you are pregnant or breastfeeding, have a medical condition, or are under a clinician's care, speak to a professional before making big changes — this is general information, not medical advice.
Reference table: daily target by deficit size
The table shows how each deficit maps to an approximate weekly loss. The example targets assume a maintenance of 2,200 kcal/day — swap in your own maintenance number and subtract the deficit to get your personal target.
| Approach | Daily deficit | Example target (maint. 2,200) | Approx. weekly loss |
|---|---|---|---|
| Maintenance | 0 kcal | 2,200 kcal | 0 (weight stable) |
| Gentle deficit | –250 kcal | 1,950 kcal | ~0.25 kg / 0.5 lb |
| Standard deficit | –500 kcal | 1,700 kcal | ~0.45 kg / 1 lb |
| Firmer deficit | –750 kcal | 1,450 kcal | ~0.7 kg / 1.5 lb |
Weekly loss is approximate, based on the ~3,500 kcal per pound / ~7,700 kcal per kg guideline; real results vary with water, adherence, and metabolic adaptation. At a low maintenance, a –750 target can fall under the NHS minimums above — use a smaller deficit if so. Substitute your own maintenance calories for the example figure.
Step 4: Get enough protein to keep muscle
In a deficit your body can shed muscle alongside fat, especially if protein is low or you do no resistance training. Eating enough protein tilts the loss toward fat and protects lean tissue. Reviews of people in a calorie deficit support around 1.6–2.2 g of protein per kilogram of body weight per day (roughly 0.7–1.0 g per pound), with the higher end favoured for leaner, well-trained people.
For an 80 kg (176 lb) person that is about 128–176 g of protein a day. Muscle is not just about looks: it supports strength and helps hold your metabolic rate up as you lose weight. Once you have a calorie target, split the target into protein, carbs, and fat with our macro calculator so protein is set first rather than left to whatever remains.
Step 5: Recalculate as you go
Metabolism adapts. As you lose weight you carry less mass, so your maintenance calories drop, and your body may become slightly more efficient. This is normal, not a sign that weight loss is "broken" — but the target you set at the start will eventually stall if you never revisit it.
A reliable rhythm:
- Hold your target for 2–3 weeks and weigh yourself under consistent conditions (same time of day, similar routine).
- Judge the trend, not any single day — daily swings from water and food volume mean nothing on their own.
- If the trend has stalled and you are not yet at goal, cut another 100–200 kcal or add a little activity, then reassess.
To set expectations and a rough finish line, project a goal date with our weight-loss timeline calculator — just remember the estimate assumes steady adherence and a fixed deficit, which real life rarely delivers perfectly.
Common mistakes to avoid
- Overestimating activity. The single most common error. Picking "very active" when most of your week is desk-bound inflates your maintenance number, so your "deficit" is barely a deficit. Choose the level that matches an average week, not your best one.
- Going too aggressive. Very large deficits drain energy, cost muscle, and often end in a rebound. Slower and sustainable beats fast and abandoned.
- Not tracking. People routinely underestimate portions and forget drinks, oils, and snacks. Weighing food for a couple of weeks — or at least logging honestly — closes the gap between what you think you eat and what you actually eat.
- Eating below BMR or the safe minimum. Cutting intake beneath your resting needs, or under the NHS floors, is hard to sustain and tends to backfire.
- Never recalculating. Using the same target after losing 10 kg (22 lb) means you are no longer in the deficit you think you are.
Key sources: CDC guidance on healthy weight and steady weight loss; NHS advice on calorie targets, minimum intakes, and safe weight loss; WHO on healthy diet; NIH/NIDDK on choosing a safe weight-loss program; ACSM position stand on physical activity for weight management; the Mifflin-St Jeor resting-energy equation (1990); and peer-reviewed work on protein needs during energy restriction (Helms et al., 2014). See the full references below. General information only, not medical advice.