How This Calculator Works
BMR: what your body burns at rest
Basal metabolic rate (BMR) is the energy your body uses to keep you alive while doing nothing: breathing, circulation, temperature control and cell repair. This calculator uses the Mifflin-St Jeor equation by default, which is widely considered one of the more accurate formulas for the general population. If you enter a body fat percentage, it switches to Katch-McArdle, which is based on lean body mass and tends to suit people who are muscular or carry unusual amounts of body fat.
TDEE: your total daily burn
Total daily energy expenditure (TDEE) is your BMR multiplied by an activity factor, covering daily movement, exercise and the energy used to digest food. Activity multipliers are rough. Most people overestimate their activity level, so if your results do not match reality after two to three weeks, adjust. If you wear a fitness tracker, you can click the Daily Burn figure and enter its average instead.
Choosing a calorie deficit
A deficit is the gap between what you burn and what you eat. The common rule of thumb is that about 7,700 kcal equals 1 kg of body fat (roughly 3,500 kcal per pound). It is a useful estimate, not a law. Real weight change is affected by water, glycogen, hormones and metabolic adaptation, which is why the 12-week projection here lowers your burn as your weight drops. Moderate deficits of around 10 to 25 percent of TDEE are generally easier to sustain and are associated with better retention of muscle than very aggressive cuts.
Why protein matters when cutting
Research on resistance-trained people in a deficit generally supports higher protein intakes, often in the range of about 1.6 to 2.4 grams per kilogram of body weight per day, to help preserve lean mass. Spreading protein across several meals can help, and protein is also more filling than carbohydrate or fat. The targets in this tool scale with the size of your deficit and can be based on lean body mass if you provide a body fat percentage.
Using the meal prep planner
The planner turns your calorie and protein targets into weights of chicken breast, white rice and broccoli, with options for raw versus cooked weights and protein shakes. Raw and cooked weights differ a lot because food loses or gains water in cooking, so always weigh in the same state your numbers assume. Use Auto-Fit Targets to solve for chicken and rice amounts that land close to your targets, then adjust to taste.
Limits of any calculator
Every figure here is an estimate from population averages. Track your weight and average intake for a few weeks, compare against the prediction, and adjust. If you have a medical condition, are pregnant, or have a history of disordered eating, speak to a doctor or accredited dietitian instead of relying on a calculator.