Subtract average intake from estimated maintenance
If estimated maintenance is 2,400 calories per day and average intake is 2,000, the arithmetic difference is 400 calories per day and 2,800 across seven days.
Read how to calculate a calorie deficit for a worked example and an explanation of what this number can and cannot tell you. If the result looks right but the trend is stalled, use the calorie deficit plateau checker.
The result inherits the uncertainty in both inputs
A maintenance figure from an equation, wearable, or app is a starting estimate. Food entries have uncertainty too. A precise-looking result is not proof that your body is using exactly that amount of energy.
Use complete days for the intake average
Calculate average intake from complete logs. A blank or partly logged day should not count as zero. The weekly calorie average calculator can prepare this input.
How big a deficit is reasonable
The arithmetic will happily produce any number you ask it for, so the size is a judgement the calculator cannot make. A common general guideline for adults is a rate of loss around 0.5 to 1% of body weight per week, which for most people is a moderate deficit rather than an aggressive one.
Larger deficits are not proportionally better. Hunger, training quality, sleep and adherence all degrade as the gap widens, and a deficit you abandon after ten days achieves less than a smaller one you keep for three months. The number that works is the one you can hold while eating enough protein and enough food variety to stay well.
Rapid or medically necessary weight loss is a clinical matter and belongs with a qualified clinician or registered dietitian, not a web calculator.
Why the scale can disagree with the arithmetic
A deficit on paper does not always show on the scale, and the gap usually has a mundane cause rather than a metabolic one.
- The intake average is incomplete. Unlogged days, weekends, oil, sauces, drinks and bites while cooking all push the real average above the logged one.
- The maintenance figure was an estimate. It came from a formula and a broad activity category, and it can be out by hundreds of calories in either direction.
- Water is masking the change. New training, salt, carbohydrate intake, travel, illness and menstrual-cycle timing all move scale weight without touching body fat.
- The window is too short. A few days cannot separate signal from noise.
Audit in that order before changing anything. The weekly calorie average calculator tests the first, and after 14 to 28 days the TDEE from weight change calculator tests the second by working out the maintenance your own data implies.
Do not use the result as a weight-loss guarantee
Body weight does not respond as a fixed linear conversion. NIDDK's model accounts for changes in energy expenditure and body composition over time. Use the NIH Body Weight Planner if you want an official adult planning model and meet its stated eligibility criteria.
This calculator is educational. It is not for children, pregnancy, breastfeeding, eating-disorder treatment, or clinical nutrition planning. Speak with a qualified clinician or registered dietitian for a personal target. Stop tracking if it leads to guilt, compensatory restriction, or distress.