Ketogenic Diet Calculator

This calculator computes the fat, protein, and carbohydrate gram targets for a therapeutic (medical) ketogenic diet, the kind used under dietitian supervision for drug-resistant epilepsy, GLUT1 deficiency syndrome, and certain other metabolic disorders -- distinct from popular low-carb "keto" diets, which are far less strict. The diet's use against epilepsy dates to Russell Wilder's 1921 work at the Mayo Clinic, and its modern clinical protocol -- including the classical fat-to-protein-plus-carbohydrate ratios used here -- follows the consensus recommendations of the International Ketogenic Diet Study Group, most recently updated in 2018. The classical ketogenic ratio expresses fat grams to combined protein-plus-carbohydrate grams, most commonly 4:1 (about 90% of calories from fat) for the strictest therapeutic protocols, or 3:1, 2:1, or a more liberal ~1:1 (comparable to a modified Atkins approach) for less restrictive variants. Given a target ratio and a daily caloric goal, the calculator first sets protein at a fixed rate per kilogram of body weight (1.0 g/kg by default, a typical adult therapeutic-keto protein allocation), then solves for how many grams of fat and carbohydrate satisfy both the ratio constraint and the total calorie target simultaneously, using the standard caloric densities of 9 kcal/g for fat and 4 kcal/g for protein and carbohydrate.

A higher ratio pushes more of the total calories toward fat and squeezes the carbohydrate allowance down; a 4:1 ratio leaves very little room for carbohydrate at all, which is precisely the mechanism believed to drive the anti-seizure ketosis this diet is used to produce. That fat/carbohydrate solve is only achievable when the weight-based protein target itself fits inside the combined protein-plus-carbohydrate budget the ratio and calorie goal imply; if protein alone exceeds that budget (a real possibility at a high protein-per-kg rate, a strict ratio, and a modest calorie goal together), carbohydrate floors at zero, the achieved fat-to-protein ratio falls short of the one requested, and the calculator reports this explicitly via an achieved-ratio figure and status message rather than silently understating the ratio. The calculator also breaks the fat and carbohydrate targets down per meal, assuming three meals a day. This tool computes the macronutrient math only -- it does not replace the medical supervision, baseline labs, and gradual diet initiation (often started in a hospital) that a real therapeutic ketogenic diet requires, and does not account for micronutrient supplementation, which is essential on this restrictive an eating pattern.