Keto Macro Calculator

Computes daily targets for fat, protein, and carbohydrate to maintain ketosis given body weight, activity level, and a calorie goal. Standard ketogenic ratio is roughly 70–75% calories from fat, 20–25% from protein, and 5–10% from carbohydrate (typically under 50 g/day).

Protein is set in grams per kilogram of lean body mass; remaining calories split between fat and a fixed carb cap.

The ketogenic diet shifts metabolism from glucose oxidation to fat oxidation by limiting carbohydrate intake below the threshold where the liver produces glucose for itself; once liver glycogen depletes, ketone bodies (β-hydroxybutyrate, acetoacetate, acetone) become the primary fuel for the brain and most peripheral tissues. The clinical version of the diet was developed in 1921 at the Mayo Clinic for treating epilepsy and used a 4:1 fat-to-(protein+carb) ratio by weight. The modern weight-loss version is less strict, typically 70-75% of calories from fat, sufficient to maintain measurable ketosis without medical supervision.

A worked example: a 70 kg adult with 20% body fat (lean body mass = 56 kg) targeting a 2000 kcal/day deficit-maintenance diet. Protein at 1.5 g/kg LBM = 84 g protein × 4 kcal/g = 336 kcal. Carb cap at 25 g × 4 kcal/g = 100 kcal. Remaining 1564 kcal from fat ÷ 9 kcal/g = 174 g fat. The macro split is 78% fat / 17% protein / 5% carb. Adjusting protein up to 2.0 g/kg LBM (an athlete or muscle-building goal) shifts the split to about 75% fat / 22% protein / 3% carb, still within ketogenic range.

Limitations and individual variance matter. The 50-gram carb threshold is a population average; some lean athletes maintain ketosis at 100 g/day, while sedentary individuals may need below 20 g. The transition period (often called keto flu) typically lasts 3-7 days as the body adapts; symptoms include fatigue, headache, and irritability, mostly attributable to electrolyte loss as glycogen depletes (each gram of glycogen binds 3-4 g of water). Sodium, potassium, and magnesium supplementation reduces these symptoms significantly. Long-term sustainability is the main practical limitation; adherence rates drop sharply after 6 months in most studies.

The net carbs vs. total carbs debate has no clean answer. Net carbs subtract fiber and sugar alcohols on the theory that they don't raise blood glucose; total carbs is more conservative. Both approaches produce ketosis when applied consistently. Continuous glucose monitors and ketone meters provide individual feedback that population-level macro splits cannot. Excess protein can be converted to glucose via gluconeogenesis, so very high protein intake (above 2.5 g/kg LBM) may compromise ketosis in some people, though most individuals tolerate higher protein than the conservative recommendations suggest.