Keto Calculator
Your personal keto macros — net carbs, protein scaled to lean mass, and fat to fill your calories — for cutting, maintaining, or gaining on a ketogenic diet.
A ketogenic diet flips the usual fuel mix: carbohydrates drop low enough that your body switches to burning fat and ketones. Making that work day-to-day is a macro-arithmetic problem — and this calculator does the arithmetic properly, scaling protein to your lean mass instead of guessing from total weight.
Whether you came for a keto macro calculator or a keto carb calculator, it’s the same job: set the carb ceiling, set the protein target, and let fat fill the calories. The calculator accepts metric or imperial units and converts automatically.
How your macros are built
- Calories — Mifflin-St Jeor BMR × activity gives your maintenance; cutting takes −20%, gaining +10%.
- Net carbs stay fixed — default 25 g/day (adjustable 0–50 g). This is the lever that produces ketosis, so it doesn’t scale with calories.
- Protein scales to lean mass — 0.8 g per lb (1.76 g/kg) of lean body mass, the practical keto standard: enough to protect muscle in a deficit without stalling ketosis. This is why the calculator asks for body fat percentage.
- Fat fills the rest — whatever calories remain after carbs and protein come from fat, typically landing around 70–75% of intake.
Don’t know your body fat percentage? Estimate it with the body fat calculator first. For the standard (non-keto) macro splits, the macro calculator offers keto alongside balanced and low-carb, and the carbohydrate calculator explains net carbs on their own.
Reading the result
The macro split looks extreme next to standard dietary advice — that’s the design, not an error. The percentages matter less than the gram targets: hit the carb ceiling, the protein floor, and use fat to control total calories. Hunger on keto is usually a fat-intake problem; a stall is usually a calories problem, not a carb problem.
Honest notes
Ketosis typically starts within 2–4 days under ~50 g net carbs, often with a rough adaptation week (“keto flu” — largely electrolytes; salt, potassium, and magnesium help). As for how much weight you’ll lose, the first week’s fast drop is mostly water — glycogen holds water, and dropping carbs releases it — while the fat loss after that comes from the same calorie deficit any diet needs, not from magic. Long-term trials show keto performs about as well as other diets once adherence is equal; its real edge is appetite control for the people it suits. And the medical caveat is genuine: diabetes medication, kidney or liver disease, or pregnancy mean clinician supervision first.
Frequently asked questions
How are keto macros calculated?
Net carbs stay fixed (default 25 g — the level that keeps most people in ketosis), protein is set from your LEAN body mass at 0.8 g per pound (1.76 g/kg) to protect muscle, and fat fills whatever calories remain for your goal — a 20% deficit to cut, maintenance, or a 10% surplus to gain.
Why does the calculator need my body fat percentage?
Because protein needs scale with lean tissue, not total weight. Two people at 100 kg with 15% vs 40% body fat carry very different amounts of muscle; scaling protein to lean mass gives each the right target. If you don't know your body fat, estimate it with our body fat calculator first.
What are net carbs, and how do I calculate them for keto?
Net carbs = total carbohydrates minus fiber (and sugar alcohols), since fiber isn't digested into glucose. So a food with 12 g carbs and 5 g fiber counts as 7 g net carbs. Keto practice typically caps net carbs at 20–30 g/day; the calculator lets you set your own allowance in that range.
Is keto safe for everyone?
No. People with diabetes on medication, kidney disease, liver conditions, or who are pregnant should only attempt keto with medical supervision — carb restriction can rapidly change blood sugar and blood pressure medication needs. For everyone else, it's a legitimate dietary pattern whose long-term results depend, like any diet, on adherence.