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About this tool
Daily fat, protein and net carb targets for a ketogenic diet, from Mifflin-St Jeor BMR, your activity level and your weight goal.
The Keto Macro Calculator sets a daily fat, protein and net carb target by fixing carbohydrate first, then protein, then letting fat take every remaining calorie — the order that keeps a ketogenic diet ketogenic. Calories come from the Mifflin-St Jeor equation for resting metabolic rate, multiplied by a standard activity factor and adjusted for your goal, with 4 kcal per gram of protein and carbohydrate and 9 kcal per gram of fat. Enter a body fat percentage and protein is set from lean mass instead of total weight.
Open Keto Macro Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Net carbs are a hard budget, not a leftover, which is the whole point of a ketogenic split.
Enter body fat percentage and protein is calculated from lean body mass rather than scale weight.
Targets are held at 1,200 kcal for women and 1,500 for men rather than returning an unsafe number.
A standard ketogenic diet is generally defined as under 50 g of net carbohydrate a day, and most people use 20-30 g to reach and hold ketosis reliably. Net carbs means total carbohydrate minus fibre (and, on most labels, sugar alcohols), because fibre is not absorbed as glucose.
Roughly 1.2-2.0 g per kilogram of body weight covers most people, with the higher end for those lifting weights or in a deficit; this calculator defaults to 1.6 g/kg. Very high protein — above about 35% of total energy — can make ketosis harder to hold and is flagged when your inputs reach it.
Because carbohydrate has to stay under a fixed ceiling and protein is set by body size and training, fat is the only macro left to balance the calorie total. On a deficit your fat target will look low relative to the classic 70-75% figure — that is expected, because stored body fat supplies the difference.
No. It interacts with diabetes medication (particularly insulin and SGLT2 inhibitors), and it is not appropriate in pregnancy or with certain kidney, liver, pancreatic or gallbladder conditions. This tool is informational only — talk to a doctor or registered dietitian before starting, and never adjust medication on your own.
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