Macro Calculator

The math behind the grams

Each macro's grams come from the same three steps:

grams = daily calories × percentage ÷ kcal per gram

The energy factors are the general Atwater values that U.S. food labels are allowed to use under FDA regulation 21 CFR 101.9: 4 kcal per gram of protein, 4 per gram of total carbohydrate and 9 per gram of fat. The calculator rounds each result to the nearest gram, so the three macros can add back up to a total a few calories off your target.

How the presets compare with U.S. reference ranges

The National Academies' Acceptable Macronutrient Distribution Ranges (AMDR) for adults are 45–65% of calories from carbohydrate, 10–35% from protein and 20–35% from fat. They describe intakes associated with adequate nutrients and lower chronic-disease risk.

• Balanced (50/20/30) sits inside all three ranges.
• High protein (40/30/30) has protein and fat inside the ranges and carbohydrate 5 points below the 45% floor.
• Low carb (25/35/40) is outside the AMDR on carbohydrate (below 45%) and fat (above 35%), with protein at the 35% ceiling. Many people follow such a plan deliberately; the point is that it is a choice outside the reference ranges, not a neutral default.

The carbohydrate RDA for adults is 130 g per day, a minimum adequate intake. Low-carb at 1,500 kcal gives 94 g and at 1,800 kcal gives 113 g, both under that figure; at 2,200 kcal and above the low-carb preset clears it.

Check protein in grams per kilogram, not just percent

Percentages scale with calories, but protein needs scale with body size. The adult RDA is 0.8 g per kg of body weight (0.36 g per lb), a minimum to avoid deficiency. The 2025–2030 Dietary Guidelines for Americans, released in January 2026, suggest 1.2–1.6 g per kg per day for adults.

To check a result, divide the protein grams by your weight in kg (lb × 0.4536). A 140-lb (63.5 kg) woman eating 1,800 kcal on the balanced preset gets 90 g of protein: 90 ÷ 63.5 = 1.42 g/kg, inside the 1.2–1.6 range. The same calories on high protein give 135 g, or 2.13 g/kg, which is above the guideline range. For a larger person on a low calorie target the opposite happens, so if protein per kg comes out low, pick the high-protein preset or raise protein manually and take the calories out of carbs.

Calories per gram also explain "missing" calories

• Fiber is counted in total carbohydrate on U.S. labels but supplies less usable energy, which is why FDA also allows labels to use 4 kcal/g on carbohydrate minus non-digestible carbohydrates and sugar alcohols.
• Alcohol has about 7 kcal per gram and is not a macro in this calculator. A day with two beers can be on target for carbs, protein and fat and still over on calories.
• Rounding on labels. Nutrition labels round calories and grams, so totals logged from labels rarely match 4/4/9 arithmetic exactly. A gap of a few percent is normal.

Choosing a split

There is no single best ratio. Total calories drive weight change; the macro split influences how full you feel, how training goes and how well you keep muscle while losing weight. A practical order of decisions is: set calories, set protein from body weight, set fat at a level you can sustain (staying at or above 20% keeps it inside the AMDR), then give the rest to carbohydrate. The presets are shortcuts for that process, and the table above shows how far each one moves the grams.

Customizing a preset by hand

If none of the three splits fits, build your own with the same arithmetic. Start with protein in grams from body weight, convert it to calories, then divide what is left.

For a 180-lb (81.6 kg) man on 2,400 kcal who wants 1.6 g/kg of protein:

• Protein: 81.6 × 1.6 = 131 g → 131 × 4 = 524 kcal (22% of calories)
• Fat at 30%: 2,400 × 0.30 = 720 kcal ÷ 9 = 80 g
• Carbs get the rest: 2,400 − 524 − 720 = 1,156 kcal ÷ 4 = 289 g (48%)

That 48/22/30 split is inside all three AMDR ranges. Run the balanced preset at 2,400 kcal for comparison and it gives 300 g carbs, 120 g protein and 80 g fat, close to the custom result.

Spreading macros across meals

Dividing daily grams by the number of meals gives per-meal targets that are easier to plan. 135 g of protein over four meals is about 34 g each; 225 g of carbohydrate over three meals and a snack is roughly 60 g per meal plus 45 g for the snack. The daily total matters more than exact timing for most people, so treat per-meal numbers as a planning aid, not a rule.

If you have diabetes, kidney disease or another condition affected by diet, ask your doctor or a registered dietitian before changing your macro split.