Macro calculator: protein, carbohydrate and fat in grams

Grams per day at 2,000 kcal, split 20/50/30worked example

100 P / 250 C / 67 F

Protein (20% of energy): 100 g400 kcal
Carbohydrate (50%): 250 g1000 kcal
Fat (30%): 67 g603 kcal
Grams added back up: 2,003 kcal+3 kcal from whole-gram rounding

This split sits inside every Acceptable Macronutrient Distribution Range the IOM published for adults: protein 10–35% of energy, carbohydrate 45–65%, fat 20–35%. Being inside the range is not a score; the committee named no single best point within it.

Daily calories (kcal)Do not have a figure? The TDEE calculator estimates one, with its error band.Body weight (optional)Protein guidance from the sports-nutrition bodies is per kilogram, so this catches a split that is in range but low in grams.

Split

Sits near the middle of all three IOM ranges.

Protein %IOM range 10–35%Carbohydrate %IOM range 45–65%Fat %IOM range 20–35%Meals per dayFor the per-meal row below.

What the IOM ranges allow at 2,000 kcal a day, in grams
Macronutrient	IOM range (% of energy)	Grams at the low end	Grams at the high end	Your split
Protein	10–35%	50 g	175 g	100 g
Carbohydrate	45–65%	225 g	325 g	250 g
Fat	20–35%	44 g	78 g	67 g

Acceptable Macronutrient Distribution Ranges for adults, from the IOM's 2005 macronutrient report; grams via the Atwater general factors. The ranges are population guidance, and the report named no optimum inside them.

The protein row deserves its own page, because it is the one macronutrient with four separate published ranges expressed per kilogram of body weight — protein calculator. For the calorie figure that goes in at the top, see the TDEE calculator.

This turns a daily calorie figure into grams of protein, carbohydrate and fat using the Atwater factors of 4, 4 and 9 kcal per gram. Every preset sits inside the Acceptable Macronutrient Distribution Range the IOM published, and any custom split is checked against those percentages rather than scored.

Acceptable Macronutrient Distribution Ranges (AMDR) — adults: protein 10-35%, carbohydrate 45-65%, fat 20-35% of total energy. Verified 2026-07-30 against Institute of Medicine, Dietary Reference Intakes for Macronutrients (2005) (A range for populations, expressed as a share of energy. The committee set no single optimum inside it, so a split being inside the range is not a score.)
Atwater general factors (energy per gram) — protein 4 kcal/g, total carbohydrate 4 kcal/g, total fat 9 kcal/g. Verified 2026-07-30 against Merrill and Watt, USDA Agriculture Handbook No. 74 (General factors, rounded for practical use. Specific Atwater factors differ by food, so whole-gram targets will not reconcile to a calorie figure exactly - the residue is shown rather than hidden.)

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Frequently asked questions

How do you calculate macros?

Split a calorie figure into percentages, then divide each share by its energy per gram: 4 kcal for protein, 4 for carbohydrate and 9 for fat. At 2,000 kcal a 20/50/30 split is 100 g protein, 250 g carbohydrate and about 67 g fat.

What macro split does the evidence support?

Rather than one split, the IOM published ranges: protein 10 to 35 percent of energy, carbohydrate 45 to 65 percent and fat 20 to 35 percent for adults. No single point inside those ranges was named as optimal, so every preset here sits inside them and none is marked as the best one.

Why do the grams not add back up to my calories exactly?

Because grams are whole numbers and the Atwater factors are rounded general values that vary by food. The residue is usually a few kcal, and this tool shows it instead of quietly absorbing it.

Should I set protein by percentage or by body weight?

Both, and then compare. Protein guidance from the sports-nutrition bodies is per kilogram of body weight, while the IOM range is a share of energy. Enter your weight and this page shows your protein share in both terms, which is how you spot a split that is technically in range but low in grams.

Is a very low carbohydrate split available here?

Not as a preset, for one reason: below 45 percent of energy you are outside the range this page cites, so a preset would put our name on a number the IOM did not publish. You can still enter any split manually and the tool will say exactly which parts fall outside the published range.

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The next number

No body metric means much on its own. Here is what this one feeds into.

Protein calculatorThe four published protein ranges are per kilogram of body weight, which is a stronger anchor than a percentage.Water intake calculatorOne of the two hydration conventions is stated per calorie, so the calorie figure on this page feeds it directly.

Related calculators

Protein calculatorNutrition targets TDEE calculatorMetabolism Maintenance calorie calculatorMetabolism

Every formula on this page is listed with its source on the methodology page, and changes to any reference value are logged in the data changelog. Canonical URL: https://myhealthmywellness.com/macro-calculator