References: Mifflin–St Jeor study, CDC adult BMI categories and Health Canada macronutrient reference ranges.
How to use the calorie calculator
Select the sex used by the formula, age, height, weight and a typical activity level. Choose maintenance, weight loss or weight gain, then select Calculate calories. You can use kilograms and centimetres or pounds, feet and inches.
Body-fat percentage is optional for Mifflin–St Jeor and required for Katch–McArdle. If you do not know it, leave it blank rather than guessing. The tool accepts ages 18–100, but its input limits do not establish that an estimate is appropriate for every person.
Resting energy and total daily expenditure
The shared calculation uses Mifflin–St Jeor: 10 × weight in kg + 6.25 × height in cm − 5 × age, plus 5 for the male formula or minus 161 for the female formula. The original study included adults aged 19–78.
Katch–McArdle uses 370 + 21.6 × estimated lean mass in kg. Lean mass is calculated from the entered weight and body-fat percentage. Measurement error in body fat therefore affects this estimate.
TDEE is resting energy multiplied by the selected activity factor: 1.2, 1.375, 1.55, 1.725 or 1.9. Optional steps, workouts and work pattern only check the consistency of that choice; they do not add exercise calories again.
Maintenance, deficit and surplus
Maintenance uses estimated TDEE. A deficit or surplus applies your selected percentage, from 1% to 25%. The comparison table shows several possible adjustments; it is not a prescription.
The display has a technical floor of 1,000 kcal/day and warns when the raw calculation falls below it. This floor is not a safe minimum intake recommendation. If it is applied, the displayed target no longer equals the requested percentage adjustment. Low targets need individual professional assessment.
The displayed target range of ±5% and maintenance range of ±10% are simple arithmetic bands used by this tool, not measured confidence intervals. A goal weight is shown for comparison; no exact date of reaching it is predicted.
Macros, meals and weekly estimates
Choose balanced (20/30/50), higher protein (30/25/45), higher carbohydrate (15/25/60) or a custom split. The numbers represent percentages of energy from protein, fat and carbohydrate in that order.
A custom split must total 100%, with protein 10–35%, fat 20–35% and carbohydrate 45–65%. Grams use 4 kcal per gram of protein or carbohydrate and 9 kcal per gram of fat. The weekly figure is the daily target multiplied by seven; the per-meal figure divides it equally by your selected meal count.
Interpreting BMI and body-fat figures
BMI is weight in kilograms divided by height in metres squared. It is a screening measure and does not distinguish fat from muscle. CDC’s adult categories are for ages 20 and older; they should not be used as an individual assessment for an 18- or 19-year-old.
The tool also shows traditional body-fat reference bands when a percentage is entered. These depend on the classification and measurement method and are not diagnostic thresholds or automatic instructions to lose fat.
Copying, printing and limitations
Copy result includes the daily target, RMR/BMR, TDEE, BMI and macro grams. Print opens your browser’s print dialog, where a Save as PDF option may be available. Entered values and results are kept for the current page session, not saved as a personal profile.
This calculator is not designed for children, pregnancy or breastfeeding. Medical conditions, eating disorders and other individual circumstances require guidance from a qualified clinician or registered dietitian. Treat every output as an estimate, not a measurement of metabolism or a personalised diet.