The daily deficit arithmetic
This calculator subtracts weekly target loss times 7,700 kcal per kilogram, divided by seven days, from maintenance intake. At 2,400 kcal maintenance and 0.5 kg/week, the daily subtraction is 550 kcal and the displayed target is 1,850 kcal/day. The 7,700 figure is a planning approximation, not a guarantee of tissue change.
Why weight does not follow a straight line
Body mass also shifts with water, glycogen, digestive contents, menstrual cycle, and sodium intake. As body size, activity, and intake change, energy expenditure can change too. A repeated weekly scale trend may therefore differ from the line implied by the starting calculation.
Maintenance drives the output
The output inherits any error in the maintenance estimate. If 2,400 kcal is only a guess, the target is also only a scenario. Use dated intake and weight records, not an isolated day, before treating the maintenance number as a useful baseline.
When not to use a generic target
Children, teenagers, pregnancy, breastfeeding, diabetes treatment, a history of disordered eating, unexplained weight change, and medical conditions should not be managed from a generic deficit equation. Seek qualified guidance for symptoms or a plan that affects health or medication.
Review rather than force the plan
Record the target, the assumed maintenance value, and the chosen weekly rate. Revisit those assumptions if energy, mood, training recovery, or weight trend changes rather than repeatedly cutting calories to force a predicted timeline.
Check the arithmetic in context
The default example produces 1,850 kcal/day because 0.5 multiplied by 7,700 equals 3,850 kcal per week, and 3,850 divided by seven is 550. Showing the intermediate numbers helps catch a common mistake: subtracting the whole weekly amount from one day. A projected rate is not a deadline. Change in weight should be reviewed with sufficient time and context, not judged by the next morning's scale value.
Energy content of weight change is not a fixed personal conversion. Early changes can reflect glycogen and water, and prolonged changes can alter expenditure and appetite. The equation is therefore best used to make a modest, reviewable scenario rather than to promise an exact number of kilograms on a calendar date.
It is informational only and is not medical or professional advice.