Macro Calculator
Split daily calories into protein, carbs and fat.
Results update as you type.
This calculator provides estimates based on population research. Results are not medical advice. Consult a qualified healthcare provider before making health or nutrition decisions.
How it works
Macronutrients, the protein, carbohydrate and fat in your diet, are what actually supply your calories, and a macro calculator splits a daily calorie figure into gram targets for each of the three. This matters because the same calorie total can be assembled in very different ways, and the balance influences muscle retention, energy levels, satiety and how well a diet fits your life. The conversion rests on the Atwater energy factors, the values chemist Wilbur Atwater established over a century ago by burning foods in a calorimeter and measuring digestibility: protein and carbohydrate each yield about 4 kilocalories per gram, fat about 9. Those same factors underpin the U.S. Dietary Guidelines and every nutrition label. This macro calculator takes your calories, applies the percentage split you choose, and divides each share by the right energy factor to return grams. People use a macro calculator to structure a diet around a goal: a higher-protein split to hold muscle while cutting, a lower-carb or keto split by preference, or a balanced split for general eating. Because protein and carbs share the same energy density while fat carries more than double, shifting the ratio changes the gram amounts substantially. Treat these gram figures as flexible daily targets to aim near, not rigid quotas you must hit to the gram.
Protein & carbs = 4 kcal/g, fat = 9 kcal/g; grams = calories × ratio ÷ kcal-per-gram
Each macro is converted using its Atwater factor, the energy it releases when metabolised. Protein and carbohydrate yield about 4 kcal per gram and fat about 9, because fat's chemical bonds store more than twice the energy. To find grams, the calculator takes each macro's share of calories and divides by its factor, so a 300 kcal fat allotment becomes about 33 g while 300 kcal of carbs becomes 75 g.
Source:U.S. Dietary Guidelines / Atwater energy factors
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter daily calories and macro split.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Protein updates instantly as you type — no button to press.
Frequently asked questions
Which macro split is best for weight loss?
No single ratio is magic; total calories drive fat loss, and the best split is the one you can sustain. That said, a higher-protein split helps most when dieting, because protein preserves muscle in a deficit and keeps you full. Beyond hitting adequate protein, whether you favour carbs or fat is mostly personal preference and performance. Pick the balance that leaves you satisfied and energetic enough to stay consistent.
Why does fat have 9 calories per gram?
Fat is more energy-dense because its molecular structure, long chains of carbon and hydrogen with little oxygen, stores more chemical energy per gram than protein or carbohydrate, which each release about 4 calories. This is why the body uses fat as its main long-term energy reserve. It also means fatty foods pack more calories into a smaller volume, worth remembering when portioning oils, nuts and butter.
Do I need to hit my macros exactly?
No. Getting within about five to ten grams of each target is more than enough for any practical goal. Chasing perfect precision daily adds stress without real benefit, since your needs vary a little day to day anyway. Protein is the macro worth prioritising; carbs and fat can flex around it based on the day's meals. Treat the numbers as a helpful guide, not a strict rulebook.
What is a good macro split for building muscle?
Prioritise protein first, around 1.6 to 2.2 g per kilogram, then fill remaining calories with enough carbohydrate to fuel training. A balanced split of roughly 40 percent carbs, 30 percent protein and 30 percent fat works well for many, though carbs often go higher for those training hard. The key is a modest calorie surplus with ample protein; the exact carb-to-fat balance is largely preference.
How do I count macros for mixed or packaged foods?
Read the nutrition label, which lists protein, carbohydrate and fat per serving, and log the amount you actually eat. For whole foods without labels, a food-tracking app with a database handles the lookup. Weighing portions with a kitchen scale is far more accurate than eyeballing, especially for calorie-dense foods. Over time you will learn common values and can estimate familiar meals quickly and reliably.