Free Tool
Body & Macro Calculator
Work out your BMI, daily calorie needs, and a macro split built around your goal — including a keto option.
Suggested daily macros
This tool gives general estimates for healthy adults and isn't a substitute for advice from a doctor or dietitian — particularly if you're pregnant, have a medical condition, or are under 18.
Macro Calculator: Find Your BMI, Calories, and Macros
This macro calculator helps you work out three things at once: your Body Mass Index (BMI), your daily calorie needs, and a personalized breakdown of protein, carbs, and fat based on your goal. Whether you're trying to lose weight, build muscle, or follow a keto diet, this tool gives you numbers to start from — no sign-up, no email required.
How this macro calculator works
The calculator uses the Mifflin-St Jeor equation, considered one of the most accurate formulas for estimating resting metabolic rate (verified by the Academy of Nutrition and Dietetics). It combines your age, sex, height, and weight to estimate your Basal Metabolic Rate (BMR) — the calories your body burns at rest — then multiplies that by your activity level to get your Total Daily Energy Expenditure (TDEE), or maintenance calories.
From there, this macro calculator applies a protein, carb, and fat split based on the goal you choose:
- Maintain weight — a balanced 30/40/30 split
- Lose weight — higher protein to help preserve muscle in a calorie deficit
- Build muscle — extra carbs to fuel training, moderate surplus
- Keto split — roughly 75% fat, 20% protein, 5% carbs, in line with standard ketogenic guidelines
Why use a macro calculator instead of guessing
Most people who try to lose or gain weight without tracking macros either eat too little protein (leading to muscle loss) or underestimate their calories entirely. A macro calculator removes the guesswork by tying your targets to your actual body stats and activity level, rather than a generic "2,000 calories a day" rule that ignores individual differences.
Understanding your BMI result
BMI is a quick screening tool, not a diagnosis. It doesn't account for muscle mass, so very muscular people can show a higher BMI despite low body fat. Still, it's a useful starting point, and this calculator shows you exactly where you fall — underweight, healthy range, overweight, or obese — based on the same ranges used by the World Health Organization.
Frequently asked questions
What is a good macro split for keto?
A standard ketogenic macro split is around 75% fat, 20% protein, and 5% carbs. This keeps carbohydrate intake low enough to shift your body toward ketosis.
How accurate is a macro calculator?
It's an estimate based on population-level formulas, typically accurate within 10% for most healthy adults. Actual results vary based on genetics, muscle mass, and sleep, so treat it as a starting point, then adjust after two weeks based on real progress.
Do I need to hit my macros exactly every day?
No — most people do well aiming within 5–10 grams of each target rather than hitting it precisely, since day-to-day variation is normal.
Is a calorie deficit of 500 safe for everyone?
For most healthy adults, yes, but pregnant people, people under 18, or anyone with a medical condition should check with a doctor before changing their calorie intake significantly.