A Target You Can Actually Hold
Weight change follows energy balance: eat less than you spend and you lose, eat more and you gain. The part that trips people up is not the principle but the size of the adjustment. A deficit large enough to feel dramatic is usually one that collapses within a fortnight, taking the result with it.
This calculator estimates what you burn in a day from your height, weight, age, sex and activity level, then applies your goal to produce a daily target you can work to.
How to Set Your Calorie Target
The activity level does more damage than any other input when it is wrong, so be conservative with it.
- Enter height, weight, age and sex. These give the basal rate the rest of the calculation is built on.
- Be conservative with the activity level. Desk work plus three gym sessions a week is "lightly active", not "very active", and the gap between those two settings is several hundred calories.
- Pick your goal: lose, maintain or gain. Maintenance is the number that keeps your weight where it is.
- Read the daily target. For loss, a deficit of 15 to 20 per cent below maintenance is sustainable for most people; larger deficits are harder to hold and cost more muscle.
- Track your actual weight for two to three weeks and compare it against what the target predicted. That comparison, not the formula, is what tells you your real maintenance level.
- Adjust as your weight changes. A smaller body burns less, so a target set ten kilos ago will stall you eventually.
Why the 7,700 Calorie Rule Overpromises
A kilogram of body fat stores roughly 7,700 calories, which suggests a 500-calorie daily deficit yields half a kilo a week indefinitely. It does not. As you lose weight your maintenance falls, because a smaller body costs less to move and maintain, so a fixed deficit shrinks in relative terms as you go. Real loss curves flatten rather than continuing in a straight line.
The other complication is that the scale measures more than fat. Glycogen binds water at roughly three grams per gram, so a change in carbohydrate intake can move the scale two kilos in a few days with no change in body fat at all. That is why weekly averages are more informative than daily readings, and why the first week of any diet exaggerates the result.
Deficit Size and What It Costs
Applied to a 2,400 calorie maintenance level, which is typical for a moderately active adult male.
| Approach | Deficit | Daily target | Loss per week | Trade-off |
|---|---|---|---|---|
| Maintenance | 0% | 2,400 | none | Weight stable |
| Slow loss | 10% | 2,160 | ~0.25 kg | Easy to sustain, muscle preserved |
| Moderate loss | 20% | 1,920 | ~0.5 kg | The usual recommendation |
| Aggressive | 30% | 1,680 | ~0.75 kg | Hunger, fatigue, more muscle lost |
| Very aggressive | 40% | 1,440 | ~1 kg | Rarely sustained; often rebounds |
| Lean gain | +10% | 2,640 | +0.25 kg | Slower, less fat gained |
Weekly figures assume the deficit is held every day, which almost nobody manages. A 20 per cent deficit followed five days out of seven beats a 40 per cent deficit abandoned in week two, and this is the main reason moderate targets outperform aggressive ones in practice.
What Calorie Targets Leave Out
Total calories decide weight, but not everything else. Protein intake affects how much of the loss comes from muscle rather than fat, and resistance training affects it more. Fibre and protein also make a given calorie target far easier to stick to, which is a practical advantage rather than a metabolic one.
This calculator gives general estimates and is not medical or dietary advice. Very low intakes, pregnancy and breastfeeding, growth in under-eighteens, and any condition affecting metabolism or nutrition all need individual guidance. If you have a history of disordered eating, calorie tracking can be counterproductive, and a clinician is the right person to advise on the approach.