IIFYM Calculator

IIFYM is the shorthand for flexible dieting. Instead of ruling foods in or out, it sets three daily numbers — protein, carbohydrate and fat in grams — and treats any food as acceptable so long as the day’s total still lands inside those numbers. There is no “good” or “bad” food in the arithmetic; a food is simply something that either fits the remaining grams or does not. That is the whole idea, and it is why the practice starts with a calorie total split into macros rather than with a list of allowed meals.

A common way to build the split is to anchor protein first, set a fat floor next, and let carbohydrate fill whatever calories are left. The three still have to reconcile back to your calorie total: multiply protein grams by 4, carbohydrate grams by 4 and fat grams by 9, add them up, and the sum should return the number you started with. That check is what keeps the split honest — carbohydrate is not a free variable, it is exactly the calories left after protein and fat are set. Size protein against body weight with the Macro Calculator, and find the calorie total to divide with the TDEE Calculator.

In practice, you log the foods you eat and subtract their protein, carbohydrate and fat from the daily targets, aiming to finish the day close to all three. The tool sets the targets; the logging is the day-to-day part, done in whatever app or notebook you prefer. It describes a way of counting, and makes no promises about outcomes. To decide whether the calorie total should sit above or below maintenance for your goal, run the Calorie Deficit Calculator before you split. These figures are general estimates for healthy adults, not medical advice.