Health & fitness
Macro Calculator
Macros — short for macronutrients — are the three nutrients that supply your calories: protein, carbohydrates and fat. This calculator splits a daily calorie target into grams of each, using a diet preset you choose. You can type your calorie target directly, or let the tool compute it from your sex, age, height, weight and activity level with the Mifflin-St Jeor equation. The math rests on a simple constant every U.S. nutrition label uses: protein and carbs each provide 4 calories per gram, and fat provides 9. Pick a balanced, high-protein, low-carb or keto split and you'll see grams and percentages update live. It runs entirely in your browser and shows the math below. This is general information only, not medical or nutritional advice — consult a licensed professional before changing your diet.
Calories & diet
Enter a calorie target
Macro splits are general templates, not a diagnosis or prescription. Individual needs vary — a dietitian can tailor them to you.
How the macro calculator works
Each macronutrient carries a fixed number of calories per gram, the same factors printed on every U.S. Nutrition Facts label. Multiply your calorie target by each macro's percentage to get its calories, then divide by its calories-per-gram to get grams.
macro math (the 4 / 4 / 9 rule)
Protein grams = (calories × P%) ÷ 4 Carb grams = (calories × C%) ÷ 4 Fat grams = (calories × F%) ÷ 9where: 1 g protein = 4 calories 1 g carbohydrate = 4 calories 1 g fat = 9 calories P% + C% + F% = 100% of your daily calories
Diet presets
- Balanced — 30% protein / 40% carbs / 30% fat. A flexible all-purpose split.
- High-protein — 40% protein / 30% carbs / 30% fat. Popular for building or keeping muscle.
- Low-carb — 40% protein / 20% carbs / 40% fat. Cuts carbs without going full keto.
- Keto — 30% protein / 5% carbs / 65% fat. Very low carb to encourage ketosis.
Notes & assumptions
- The 4/4/9 factors are rounded label values; the precise Atwater factors vary slightly by food.
- Alcohol (7 calories per gram) isn't counted as a macro here.
- Calculations are for general information only and are not medical or nutritional advice — consult a professional before changing your diet.
Worked example
Say your daily target is 2,000 calories and you pick the balanced split (30% protein, 40% carbs, 30% fat). Protein gets 30% of 2,000 = 600 calories, and 600 ÷ 4 = 150 g of protein. Carbs get 40% = 800 calories, and 800 ÷ 4 = 200 g of carbs. Fat gets 30% = 600 calories, and 600 ÷ 9 ≈ 67 g of fat. Add the calories back up — 150×4 + 200×4 + 67×9 = 600 + 800 + 603 = about 2,003 — and you're right back at your target (small rounding aside). Switch to keto and the same 2,000 calories becomes roughly 150 g protein, 25 g carbs and 144 g fat. Change any input above and every number recalculates instantly.
Frequently asked questions
What are macros?
Macros, or macronutrients, are the three nutrients your body needs in large amounts and that supply all your calories: protein, carbohydrates and fat. Protein builds and repairs tissue, carbs are your body's main energy source, and fat supports hormones and nutrient absorption. "Counting macros" means tracking how many grams of each you eat, rather than just total calories, so you can shape your diet toward a goal like building muscle or cutting carbs.
How many calories are in protein, carbs and fat?
Protein and carbohydrates each provide about 4 calories per gram, while fat provides about 9 calories per gram — more than double. Alcohol, which isn't a true macronutrient, supplies about 7 calories per gram. These rounded "4/4/9" values are the ones used on U.S. Nutrition Facts labels, and they're exactly what this calculator uses to convert your calorie target into grams of each macro.
What's a good macro split for me?
It depends on your goal. A balanced 30/40/30 split works well for general health and is easy to hit. If you're training to build or preserve muscle, a higher-protein split (around 40% protein) helps. Low-carb and keto splits shift calories toward fat and suit people who prefer that style of eating or have specific reasons to limit carbs. There's no single best answer — pick a preset that fits your goals and lifestyle, and adjust based on results.
How much protein do I really need?
General guidelines suggest roughly 0.5 to 0.8 grams of protein per pound of body weight for active adults, with the higher end favored by people doing resistance training. A 160-pound person might aim for 80 to 130 grams a day. The percentage-based splits here are a quick starting point; if you want to target protein by body weight instead, set the grams directly and adjust your other macros to fill the remaining calories. Always check with a professional for personalized targets.
Why don't my macro grams add up perfectly to my calories?
Small gaps are just rounding. The calculator rounds grams to whole numbers for readability, so multiplying them back by 4, 4 and 9 may land a few calories above or below your exact target. The percentages themselves always sum to 100%. If you need precise totals for a food-tracking app, use the gram figures as close targets rather than treating the rounded calories as exact — a difference of a handful of calories has no practical impact.