Calorie Deficit Calculator – Daily Intake, Timeline and Safety
"I want to lose 10 kg" is a wish, not a plan. This calorie deficit calculator turns it into three concrete numbers: how many calories to eat each day, how fast the weight will come off, and roughly when you will arrive. It also does the part most calculators skip — telling you honestly whether the plan you have chosen is sensible.
The Three-Step Chain: BMR → TDEE → Target
Every credible calorie target is built from the same chain. BMR (basal metabolic rate) is what you burn at complete rest — the cost of simply being alive, and usually 60–70 % of your daily total. The default Mifflin–St Jeor equation estimates it as (10 × kg) + (6.25 × cm) − (5 × age) + 5 for men and − 161 instead of + 5 for women.
Multiply BMR by an activity factor — 1.2 for a desk job up to 1.9 for a physical job or twice-daily training — and you get TDEE, your maintenance calories. Eat that and your weight holds. Subtract a deficit and you lose; add a surplus and you gain. The calculator exposes every one of these intermediate values rather than hiding them behind a single headline figure.
Turning a Rate Into Calories
The bridge between kilograms and calories is the convention that a kilogram of body tissue stores about 7,700 kcal (roughly 3,500 kcal per pound). That gives the core formula:
daily deficit = (weekly rate in kg × 7,700) ÷ 7, so a target of 0.5 kg/week needs a deficit of 550 kcal/day, and target intake = TDEE − deficit.
Because any two of rate, deficit and timeline determine the third, you can enter whichever you actually know. Give a goal weight and a deadline and the tool back-solves the deficit that deadline demands — then tells you if that deficit is unrealistic, rather than silently returning a starvation number.
Where the Safety Limits Come From
A deficit is a stress, and past a point the cost outweighs the speed. Three independent guardrails apply here. The intake floor of 1,200 kcal for women and 1,500 kcal for men is the conventional lower bound for unsupervised dieting; below it, meeting micronutrient needs becomes genuinely difficult. The deficit ceiling flags anything above 25 % of TDEE and refuses to endorse above 40 %. The rate ceiling watches weekly loss as a percentage of body weight, because 1 kg/week means something very different at 120 kg than at 55 kg.
Why Real Results Lag the Model
A straight line on a weight chart is a fiction, and pretending otherwise is why people quit. Three things bend the curve. Metabolic adaptation: as you shrink, maintenance falls, so a fixed intake produces a shrinking deficit. NEAT — the fidgeting, pacing and general restlessness that is not deliberate exercise — quietly declines when you are eating less. And intake under-reporting is close to universal; studies routinely find people eat several hundred calories more than they record. Switch on the adaptive TDEE option to see the realistic flattening curve plotted against the naive straight line.
Water weight adds noise on top of that. Glycogen binds roughly three grams of water per gram, so the first week of any diet shows a dramatic drop that is mostly not fat — and a single salty meal can mask a fortnight of genuine progress on the scale.
Beyond the Headline Number
A calorie target alone is a blunt instrument. The macronutrient split divides your intake into protein, fat and carbohydrate — protein set in g/kg of body weight, fat as a percentage of calories, carbohydrate taking the remainder. Keeping protein high (1.6–2.2 g/kg is the common evidence-based range) is the single most effective way to protect lean mass while dieting.
The diet versus exercise split lets you meet part of the deficit by moving more rather than eating less, and refeed days redistribute the same weekly deficit across fewer days, so a 550 kcal daily deficit becomes a steeper deficit on six days with one day at maintenance. The weekly total — and therefore the projected outcome — is unchanged; only the day-to-day experience differs.
Finally, the tool shows your maintenance calories at goal weight. That number matters more than the deficit, because it is what you will be eating for the years after the diet ends — and knowing it in advance is the difference between finishing a diet and keeping the result.