Free keto macro calculator
Calculate your daily calories, fat, protein, and net carbs for keto in 30 seconds, adjusted for your age, sex, activity, and chosen keto mode.
Cetona's keto macro calculator gives you in under a minute the exact daily split of calories, fat, protein, and net carbs you need to enter ketosis and stay there. Unlike generic calculators that apply the same formula to everyone, ours adjusts your macros based on your age, sex, activity level, and goal (weight loss, maintenance, energy, or health).
It's built for beginners who finally want to know how many net carbs they can eat per day, and for experienced ketoers who want to fine-tune their fat-to-protein ratio or pick between strict (20 g), lazy (35 g), and cyclical (50 g) keto. No email required to see your result, no signup, no paywall.
Calculate your macros below
The form takes 30 seconds and works without signup.
Aim for a moderate loss (5-12% of current weight) to preserve muscle and avoid yo-yo dieting.
⚠️ Health floor: we don't go below 50 kg (BMI 18.5) for your height.
Free • No signup required
How it works
1. Enter your basics
Sex, age, weight, and height. Toggle between kg/cm and lb/ft+in as you prefer. Your data stays local during the calculation, nothing is sent without your consent.
2. Pick your activity level
Sedentary, light, moderate, or active. This is the single biggest driver of your total daily energy expenditure (TDEE), so take 5 seconds to pick the right one.
3. Set your goal
Lose weight, maintain, more energy, or better health. For weight loss, the deficit is scaled progressively against your target weight (5 to 25%).
4. Select your keto mode
Strict 20 g (fast ketosis), lazy 35 g (more veggie variety, more sustainable long-term), or cyclical 50 g (for explosive athletes: CrossFit, HIIT, running).
5. Get your macros instantly
Calories, fat, protein, net carbs, BMI, safety floor, electrolyte targets, and per-meal protein goal. Email yourself the summary or jump straight to a personalized 7-day keto plan.
Why our macros are more accurate
Most keto calculators use the Mifflin-St Jeor formula and apply a flat 75/20/5 ratio. That works for a sedentary 30-year-old woman, much less for a 55-year-old wanting to preserve muscle mass or an endurance athlete.
Age and sex adjustment
After 50, protein needs rise significantly (sarcopenia, age-related muscle loss). Our calculator bumps the protein ratio and shows a per-meal protein target high enough to hit the leucine threshold (~2.5 g) that triggers muscle protein synthesis.
Safety floor at 1200/1500 kcal
We never recommend going below 1200 kcal/day for women or 1500 kcal/day for men, in line with the Academy of Nutrition & Dietetics and EFSA guidelines. Below that, muscle loss, metabolic slowdown, and deficiencies are almost guaranteed.
Three keto modes, not one
Strict, lazy, or cyclical, depending on your profile. Many people fail at keto because they're forced into 20 g of carbs when 35 g would let them stick to it for 6 months instead of 6 days. The best mode is the one you'll actually keep.
BMI 18.5 floor on target weight
The target weight slider automatically blocks at the WHO underweight threshold (BMI 18.5) for your height. We never let you target a goal below that line, regardless of your current weight.
Anti keto-flu kit included
Alongside your macros, you get the exact electrolyte intakes to aim for (sodium, potassium, magnesium) to avoid keto flu (fatigue, headaches, cramps), the number-one reason 80% of beginners quit during week one.
Frequently asked questions
Is the calculator really 100% free?
Yes. You get your full macros with no email, no signup, and no paywall. The email option is only offered if you want a copy of the summary plus our keto starter guide, but the on-screen result is entirely open.
What formula do you use?
We use the Mifflin-St Jeor formula for basal metabolic rate (BMR), validated as the most accurate for adults in a 2005 American Dietetic Association meta-analysis. TDEE uses the standard Harris-Benedict activity coefficients (1.2 to 1.725).
Why are my net carbs so low (20-50 g)?
Nutritional ketosis (your body producing ketones) generally starts below 50 g of net carbs per day, and is faster and more stable below 20 g. Net carbs = total carbs minus fiber minus certain polyols. We count nets because fiber has no meaningful impact on blood glucose.
How often should I recalculate my macros?
Every 5 kg or 11 lb lost or gained. As you lose weight, your body needs fewer calories to function (less mass to maintain), so sticking with the old numbers slows progress. If your activity level changes (new sport, injury), recalculate too.
Is keto safe for everyone?
No. Keto is contraindicated during pregnancy, breastfeeding, with type 1 or treated type 2 diabetes, with kidney or liver disease, with eating disorders, and under 18. Talk to your doctor before starting if you take insulin or blood-sugar medications.
Is my data shared?
No, never. Your inputs (weight, height, age) are used only for the on-screen calculation. If you voluntarily enter your email to get the summary, you can unsubscribe with one click. See our Privacy Policy page for full GDPR details.
Go deeper
Complete articles to dive in once you have your macros.
How many carbs per day on keto?
The exact threshold to enter ketosis, how to tune it for your profile, and why 20 g isn't mandatory for everyone.
Net carbs vs total carbs: what to count
How to read a keto-friendly nutrition label, which polyols to count, which fibers to subtract, and why countries label differently.
Keto and weight loss: what the science says
Meta-analysis of clinical trials on nutritional ketosis, caloric deficit on keto, and 6 and 12-month outcomes.
Complete keto electrolyte guide
Exact sodium/potassium/magnesium doses to avoid keto flu, food sources, and recommended supplements.