About the Keto Calculator
This keto calculator sets up your daily macros for a ketogenic diet. It estimates your maintenance calories with the Mifflin-St Jeor equation and your activity level, applies the calorie deficit or surplus you choose, then fills your plan in the order keto dieters usually build it: a fixed net-carb limit first, protein based on your lean body mass second, and the remaining calories from fat.
It suits anyone starting keto for weight loss, people who already eat low carb and want precise numbers, and those checking whether a keto meal plan is balanced. Most people reach ketosis with 20–50 g of net carbs a day; 20–30 g is the strict range often used when starting out.
Protein is set per kilogram of lean body mass (your weight minus fat mass), so enter an honest body-fat estimate. Fat is treated as a lever: it fills whatever calories are left, so if you are losing weight you do not need to hit the fat number exactly — protein and carbs are the targets that matter. Talk to a doctor first if you take diabetes or blood-pressure medication.
With the default inputs, the daily calories is 2,033 kcal. Change any value above to recalculate instantly.
How to use the keto calculator
- 1Enter your sex, age, height, weight and an estimate of your body fat percentage.
- 2Choose your activity level and goal (deficit, maintenance or surplus).
- 3Set your net carb limit — 20–30 g for strict keto.
- 4Adjust protein per kg of lean mass if you train hard or want to preserve more muscle.
- 5Track net carbs and protein daily and use fat to reach fullness, up to the fat target.
Formula and method
Maintenance calories come from the Mifflin-St Jeor equation times your activity factor, then are reduced or increased by the goal percentage. Net carbs are fixed at the limit you choose. Protein is lean body mass — weight × (1 − body fat %) — multiplied by your chosen grams per kilogram, commonly 1.2–2.0 g/kg of lean mass on keto.
Fat fills the remaining calories using 9 kcal per gram, while carbohydrate and protein count 4 kcal per gram. Net carbs are total carbohydrates minus fibre (and usually sugar alcohols such as erythritol), which is how most keto food labels and apps count them.
- BMR
- Basal metabolic rate (Mifflin-St Jeor)
- lean mass
- Body weight × (1 − body fat % ÷ 100)
- ratio
- Protein grams per kg of lean mass
Worked examples
35-year-old man, 5 ft 10 in, 200 lb, 25% body fat, lightly active, 20% deficit
His maintenance is about 2,542 kcal, so a 20% deficit gives about 2,033 kcal. Lean mass is 200 × 0.75 = 150 lb (68 kg), so protein is 68 × 1.6 ≈ 109 g. After 25 g of net carbs (100 kcal) and 435 kcal of protein, the remaining ~1,498 kcal is about 166 g of fat — roughly 74% of calories.
40-year-old woman, 165 cm, 75 kg, 32% body fat, sedentary, 10% deficit, 20 g carbs
BMR = 10 × 75 + 6.25 × 165 − 5 × 40 − 161 ≈ 1,420 kcal; × 1.2 gives 1,704 kcal maintenance and 1,534 kcal after a 10% cut. Lean mass is 51 kg, so protein is 76.5 g. Subtracting 80 kcal of carbs and 306 kcal of protein leaves about 128 g of fat.
Maintenance with 50 g net carbs
At maintenance (about 2,542 kcal), 50 g of net carbs is 200 kcal or about 8% of calories — still within typical keto limits. With 109 g of protein, fat rises to about 212 g a day.
Frequently asked questions
How many carbs can I eat on keto?+
Most people reach and stay in ketosis at 20–50 g of net carbs a day. Starting at 20–30 g is common because it works for almost everyone; some active people can later go a little higher and remain in ketosis.
What are net carbs?+
Net carbs are total carbohydrates minus dietary fibre, and usually minus sugar alcohols like erythritol. Fibre is not digested into glucose, so it has little effect on blood sugar or ketosis.
How much protein should I eat on keto?+
A common target is 1.2–2.0 g per kg of lean body mass. Eating enough protein protects muscle while dieting; moderate excess is unlikely to stop ketosis for most people despite the popular worry about gluconeogenesis.
Do I have to eat all my fat grams?+
No. On a weight-loss keto plan fat is the flexible macro: hit your protein and stay under your carb limit, then eat fat until satisfied. Eating less fat than the target simply increases your calorie deficit.
What is the typical keto macro ratio?+
A standard ketogenic diet is roughly 70–80% of calories from fat, 15–25% from protein and 5–10% from carbohydrate. Your exact percentages depend on your calories, lean mass and chosen carb limit.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.