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The calculator starts from your daily calorie target and your goal (cut, maintain or bulk, which presets a sensible protein target and fat percentage that you can still adjust). It first locks in protein: your protein target in grams multiplied by 4 kcal per gram. Whatever calories remain are split between fat and carbohydrate: fat gets your chosen percentage of the remainder, divided by 9 kcal per gram, and carbohydrate takes everything left, divided by 4. Every result shows grams alongside the calories that macro contributes, so you can verify the arithmetic adds back up to your daily target. These are nutrition estimates for planning, not medical or dietetic advice. If you have a medical condition, take medication affecting appetite or metabolism, are pregnant, or have a history of disordered eating, work with a doctor or registered dietitian instead of a calculator.
Macronutrients, usually just called macros, are the three nutrients that supply calories: protein, carbohydrates and fat. Each has a fixed energy density: protein and carbohydrate carry about 4 kilocalories per gram, while fat carries about 9 kilocalories per gram. Tracking macros instead of only calories gives you finer control over body composition, because the same 2,000 calories built mostly from protein supports muscle very differently from 2,000 calories built mostly from sugar. A macro split is simply your daily calorie target divided into grams of each of the three, and this calculator does that division for you.
Enter your daily calorie target, pick your goal (cut, maintain or bulk), set your daily protein target in grams, and set the percentage of your remaining calories that should come from fat. The calculator first reserves protein (protein grams × 4 kcal), then assigns fat from the remaining calories (fat percent / 9), and finally fills everything left with carbohydrate (remaining / 4). Results show each macro in grams per day, plus the calories each one contributes, so the arithmetic is fully visible.
Protein grams = your protein target (set directly, in grams) | Protein calories = protein grams × 4 | Remaining calories = total calories - protein calories | Fat grams = remaining calories × fat % / 100 / 9 | Carbohydrate grams = remaining calories × (1 - fat % / 100) / 4 | Check: (protein g × 4) + (carbs g × 4) + (fat g × 9) = total calories. These energy densities (4, 4, 9) are the standard Atwater values used across nutrition science. These energy densities are the formula the calculator applies to every result on this page.
Evidence-based guidance anchors protein to body weight rather than to a percentage of calories, because your body's protein need does not change with your calorie target. Common targets: around 1.6 to 2.2 grams per kilogram of body weight for people training or dieting, with the higher end (up to about 2.4 g/kg) during a cut to preserve muscle, and about 1.8 to 2.0 g/kg during a bulk, where the surplus itself supports muscle growth. Set your protein target first in the calculator, then let fat and carbohydrate divide the rest. Percentage-only splits fail here: 30 percent protein of 1,800 calories is 135 g, but of 2,600 calories it is 195 g, while your body's requirement stayed the same.
A 2,000 kcal day with a 150 g protein target and 30 percent of the remainder to fat: protein calories = 150 × 4 = 600; remaining = 1,400; fat = 1,400 × 0.30 / 9 = 46.7 g (420 kcal); carbs = 1,400 × 0.70 / 4 = 245 g (980 kcal). Total check: 600 + 420 + 980 = 2,000. A 2,500 kcal maintenance day with 160 g protein and 27.5 percent fat: protein 640 kcal, remaining 1,860, fat 56.8 g (512 kcal), carbs 337.1 g (1,349 kcal). You can verify every number on the page by re-running the same arithmetic.
Common presets from competitors: balanced 30/40/30 (protein/carbs/fat), high protein 35/35/30, muscle gain 30/45/25, lower carb 35/25/40. Rather than locking you into one, this calculator's fat-percentage slider lets you recreate any of these: at 2,400 kcal, 150 g protein and 30 percent fat gives you the balanced-style split. Evidence supports a wide range of splits, and adherence matters more than the exact ratio. One guardrail most plans agree on: do not drop fat below about 20 percent of calories for long periods, since fat supports hormones, satiety and absorption of vitamins A, D, E and K. Each preset is just a different macro nutrient ratio, and you can dial in any ratio you like with the fat-percentage slider.
Cutting (fat loss): set protein at the high end of your range, around 2.0 to 2.4 g/kg, because preserving muscle in a deficit needs more protein, not less. Keep fat at a floor of roughly 25 percent of calories for hormone health. Maintaining: around 2.0 g/kg protein and about 27.5 percent of calories to fat is a common middle ground. Bulking: 1.8 to 2.0 g/kg protein is usually enough, with fat near 30 percent and the extra calories flowing into carbohydrate to fuel hard training. In every goal, carbohydrate is the flexible variable: it is the fuel for training, so let it rise when training volume rises.
Dividing fat calories by 4 instead of 9 overestimates your fat grams by more than double, the single most common arithmetic error. Chasing exact grams daily is unnecessary: weekly averages matter more than daily precision, and plus or minus 10 grams is noise. Remember that fibre, vitamins and minerals are not tracked by a macro split, so food quality still matters alongside the numbers. Finally, alcohol contributes about 7 kcal per gram and fits none of the three macros: account for it against carbohydrate or fat, but it must come out of the total.
Use the fixed energy densities: protein and carbohydrate carry 4 kcal per gram, fat carries 9. First reserve protein (your protein target × 4), then compute fat as remaining calories × fat percent / 100 / 9, and carbohydrate as the rest / 4. A 2,400 kcal day at a balanced-style split gives 180 g protein, 240 g carbs and 80 g fat.
Macronutrients are the three nutrients your body needs in large amounts that supply energy: protein, carbohydrates and fat. Each carries a fixed energy density: 4 kcal/g for protein and carbohydrate, 9 kcal/g for fat. Everything else in nutrition (fibre, vitamins, minerals) rides along with them.
Common evidence-based guidance for people training or dieting is roughly 1.6 to 2.2 grams per kilogram of body weight daily, up to about 2.4 g/kg during a cut to preserve muscle. Sedentary minimums are lower, around 0.8 g/kg. Higher intakes help preserve muscle in a calorie deficit.
After reserving protein calories, multiply the remaining calories by your chosen fat percentage and divide by 9, because fat is the most energy-dense macronutrient at 9 kcal per gram. For example, 1,400 remaining calories at 30 percent fat gives 1,400 × 0.30 / 9 = 46.7 g of fat.
Research consistently finds that with calories and protein matched, low-carb and higher-carb diets produce similar fat loss. Carbohydrate is the flexible fuel variable: raise it when training hard, lower it when you prefer fewer carbs, and keep fat at a floor that supports hormones. Pick the split you can sustain.
No, treat grams as daily targets to land near, not laws. Plus or minus 10 grams is noise from food labels, cooked weights and rounding. Weekly averages matter far more than any single day, and rigid daily targets are a common route to an unhealthy relationship with food.
IIFYM stands for If It Fits Your Macros, a flexible dieting method that counts protein, carbohydrate and fat rather than restricting specific foods. Any food is allowed as long as it fits within your daily macro targets. This calculator follows the IIFYM-style method: protein first, then fat, then carbohydrate fills the rest.
About 7 kcal per gram, and it fits none of the three macro categories. Most tracking approaches account for alcohol against carbohydrate or fat: whichever you choose, its calories have to come out of the daily total, and it displaces food calories that would have carried nutrients.