Keto Calculator

A standard ketogenic macro split works backward from a fixed, low carbohydrate ceiling, rather than the percentage-based approach used on our general Macro Calculator. Carbohydrate is set first as a hard gram cap, protein is set by body weight, and fat fills whatever calories are left over¹.

What This Calculator Measures

This gives you a daily calorie target plus fat, protein, and carbohydrate grams built specifically around inducing and maintaining nutritional ketosis, not a general-purpose macro split. Carbohydrate is shown as a fixed gram target rather than a percentage, since that's how ketogenic macros are actually set in practice.

The Formula

TDEE is calculated using the Mifflin-St Jeor formula plus your activity level, the same method as the TDEE Calculator, then adjusted for your goal: 500 calories less to lose weight, but never below 1,200 calories for women or 1,500 for men (the same floor as the Calorie Calculator), or 300 calories more to gain.

Carbohydrate = fixed 20–50g net carbs/day (goal-independent)

Protein (g) = body weight (kg) × 1.3 g/kg, or × 1.6 g/kg at a moderate activity level or higher

Fat (g) = (remaining calories after protein and carbohydrate) ÷ 9

The 20–50g net carb range is the standard cited across nutritional ketosis literature and clinical practice for inducing and maintaining ketosis¹.

How This Calculator Computes Your Result

Enter your stats, activity level, and goal above. We calculate your TDEE and goal-adjusted calorie target first, subtract calories from your fixed carbohydrate cap and your body-weight-based protein target, and allocate every remaining calorie to fat.

Why Carbohydrate Is Capped So Low

Ketosis is a metabolic state where the body shifts from burning primarily glucose to burning fat and fat-derived ketones for fuel, and that shift is driven by insulin. Carbohydrate intake is the strongest driver of insulin release, so bringing carbohydrate down far enough is what allows insulin to fall enough for the liver to start producing ketones in meaningful quantities.

A 2018 review focused specifically on nutritional ketosis says research should use under 50g of carbohydrate per day, under about 10% of calories, to reliably reach this state¹. That's the basis for this calculator's 20 to 50g options: all at or under that ceiling, with lower caps for people who want more margin, since the exact cutoff differs from person to person.

The same review covers what nutritional ketosis is actually associated with once achieved: improvements in several metabolic syndrome markers, including insulin resistance, lipid profile, and inflammatory markers¹. That's the underlying rationale for why someone would choose this approach over a standard percentage-based macro split in the first place, not just a lower number on the scale, but a genuinely different metabolic state.

Why Protein Is Set Higher Than the General RDA

The general adult RDA for protein is 0.8 g/kg, but that figure is a floor meant to prevent deficiency, not a target for someone actively restricting another macronutrient.

When carbohydrate is this limited, and especially when calories are also reduced for weight loss, adequate protein becomes more important for preserving lean mass, research on protein needs during calorie restriction in resistance-trained individuals supports intakes well above the general RDA specifically to protect muscle during a deficit³.

This calculator uses 1.3 g/kg, rising to 1.6 g/kg if your activity level is moderate or higher, since regular training raises protein needs.