What the estimate can answer
The calculator applies the Mifflin-St Jeor resting metabolic rate equation to age, weight, height, and the selected equation coefficient. It then multiplies resting energy by the activity estimate to create a rough total daily energy expenditure, or TDEE, scenario. The final comparison adds or subtracts the chosen fixed daily amount.
Use the steps in order
First choose the equation inputs, then enter measurements taken in one system. Last, choose the closest activity description and the question you want to compare. If activity is uncertain, rerun a nearby level. A result that moves substantially is a sign that the assumption matters more than the displayed precision.
A calorie adjustment is not a weight forecast
The 250- and 500-calorie choices are simple arithmetic comparisons around estimated maintenance. They do not model water, glycogen, digestion, body-composition change, metabolic adaptation, illness, medication, adherence, or changing energy needs. The calculator deliberately does not convert the adjustment into promised pounds or kilograms per week.
Equation scope and uncertainty
Metric entries use kilograms and centimeters. US entries use pounds and total inches, then convert internally. The published equation uses a sex-specific coefficient; choose the coefficient that best matches the clinical input you use with a health professional. The original study included healthy adults ages 19 through 78, so this tool keeps that adult age boundary.
Formula and further context
This implementation uses the coefficients summarized in the NCBI Endotext equation table: 9.99 times kilograms plus 6.25 times centimeters minus 4.92 times age, then plus 5 for the male coefficient or minus 161 for the female coefficient. See the original Mifflin-St Jeor study and the NIDDK Body Weight Planner for deeper context.
This is an educational population-formula estimate, not a diet prescription or medical assessment. It is not intended for children, pregnancy, eating-disorder care, critical illness, or decisions requiring individualized clinical advice.