Calorie deficit calculator
Estimate a daily calorie target for a weight goal, compare a chosen weekly rate or timeline, and view a changing-weight projection.
Searching for an AI calorie deficit calculator? This one uses a standard published formula, not an AI model, so you can see exactly how your number is made. See how BiteCal AI tracks meals against it.
Estimated daily target
1,965 kcal / day
Estimated deficit 440 kcal/day · 0.40 kg/week at the starting weight
Dynamic estimate: about 24 weeks to the goal
Week-by-week estimate. Energy needs are recalculated as weight changes.
Calorie estimates are approximate and are not medical advice. Pregnancy, breastfeeding, medical conditions, or eating-disorder history warrant individual professional guidance.
Use this daily target in the macro calculator →A 7,700 kcal/kg conversion is a rough static estimate. Water and glycogen can change scale weight substantially, especially in the first weeks. Intake floors are general guardrails, not universal prescriptions. Discuss a personal plan with a qualified clinician.
Your result explained
The result estimates an intake and trajectory from the profile and activity level you enter. The simulation recalculates estimated energy needs as body weight changes; it remains a simplified model, not a guaranteed forecast.
How it’s calculated
Mifflin–St Jeor estimates BMR, then an activity factor estimates maintenance calories. A static starting estimate uses 7,700 kcal per kg of weight change; the week-by-week model recalculates expenditure at each simulated weight and stops if the modeled deficit falls below 50 kcal/day.
Worked example: At 80 kg, a 0.4 kg/week rate corresponds to about 440 kcal/day using 0.4 × 7,700 ÷ 7. The actual plan may differ because the tool applies intake guardrails and recalculates expenditure as weight changes.
Limits and accuracy
The 7,700 kcal/kg rule is a rough simplification and does not account for water, glycogen, adherence, metabolic adaptation, or individual medical factors. First-week scale changes can be driven by fluid and food-volume shifts. The 1,200/1,500 kcal intake values are general guardrails, not universal safe limits. The calculator does not provide weight-loss targets for people under 18.
Frequently asked questions
What is a calorie deficit?
A calorie deficit means energy intake is below estimated energy expenditure over time. This calculator estimates—not measures—the size of that difference.
How many calories are in a kilogram of weight loss?
The tool uses about 7,700 kcal per kg as a static planning approximation. Real weight change is dynamic and does not follow a perfectly straight line.
Can I choose a target date?
Yes. The target-date mode uses a bounded numerical search and a week-by-week simulation, then shows if the goal is not reached by the date at the general intake guardrail.
Does this calculator work for teens?
No. It blocks weight-loss planning under age 18 because growth and nutrition needs require age-specific professional assessment.
Can I share my calculator inputs?
Yes. The calculator keeps supported inputs in the page URL, so you can copy the address bar and reopen the same setup.
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BiteCal is preparing a photo-based food diary to help you review meals and nutrition estimates.
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Estimates only. This is not medical advice. Last reviewed: 20 October 2026.