Macro Calculator

A macro calculator turns a daily calorie target into grams of protein, carbohydrate and fat. Multiply calories by each share, then divide by 4 calories per gram for protein and carbs or 9 for fat. At 2,000 calories with 20% protein, 50% carbs and 30% fat, that is 400 ÷ 4 = 100 g protein, 1,000 ÷ 4 = 250 g carbs and 600 ÷ 9 ≈ 67 g fat.

How to use the macro calculator

1. Choose how to set your calories. Estimate from TDEE uses the Mifflin-St Jeor equation and an activity factor, the same method as our TDEE calculator. Enter calories lets you type a target you already have.
2. Pick a macro split. The four presets all sit inside the Acceptable Macronutrient Distribution Ranges (AMDR). Custom lets you type your own percentages.
3. Optionally set protein by body weight at the adult RDA of 0.8 g per kg instead of as a percentage.
4. Choose how many meals you eat to see grams per meal.
5. Read your grams at the top, then check the AMDR table, open Show steps for the full working, or use Copy result.

AMDR: the macronutrient ranges for adults

The Dietary Reference Intakes from the National Academies (formerly the Institute of Medicine) give each energy-providing macronutrient an Acceptable Macronutrient Distribution Range. It is a range of shares of total calories, not a single number.

Many different splits fit inside these ranges, which is why the calculator offers several presets instead of one “correct” answer. The tool is built for adults, so it checks your split against the adult column.

One honest note: in 2024 a National Academies committee concluded that the method used to set the AMDRs does not meet current evidence standards and suggested that future reviews replace them. Until a new review is published, the 2002/2005 ranges above are still the published values, and the committee advised recognizing their limits.

Macro formula: from calories to grams

Every gram of protein or carbohydrate counts as 4 calories and every gram of fat as 9. These are the general factors the FDA uses for Nutrition Facts labels. With them, the calculation has two steps for each macronutrient:

macro calories = daily calories × percent ÷ 100
grams = macro calories ÷ calories per gram

Because fat has more than twice the calories per gram, the same share of calories gives far fewer grams of fat. A 30% fat share at 2,000 calories is 600 calories but only about 67 g.

Macro split presets

Each preset adds up to 100% and keeps every macronutrient inside its adult AMDR. The names describe the numbers only; none of them is a diet or a promise of any result.

A custom split can go outside the ranges. The calculator still does the math, but it marks the macronutrient as outside the AMDR.

Protein by body weight: the RDA

The Recommended Dietary Allowance (RDA) for protein for adults is 0.8 g per kilogram of body weight. That works out to the familiar 46 g a day for women and 56 g a day for men at the reference body weights. An RDA is the daily intake that meets the needs of nearly all (97–98%) healthy people in a group. It is a reference level for healthy adults, not a personal prescription.

When you choose RDA 0.8 g/kg, the calculator fixes protein at 0.8 × your weight in kg and shares the remaining calories between carbs and fat in your chosen ratio. The tool also shows two other reference checks: the carbohydrate RDA of 130 g a day for adults, and the fiber Adequate Intake for your age and sex.

Worked macro examples

Example 1: 2,000 calories, middle split, 4 meals

1. Protein: 2,000 × 20% = 400 calories, and 400 ÷ 4 = 100 g.
2. Carbs: 2,000 × 50% = 1,000 calories, and 1,000 ÷ 4 = 250 g.
3. Fat: 2,000 × 30% = 600 calories, and 600 ÷ 9 ≈ 66.7, about 67 g.
4. Per meal: 100 ÷ 4 = 25 g protein, 250 ÷ 4 = 62.5 g carbs and 66.7 ÷ 4 ≈ 17 g fat.

Example 2: from TDEE, more protein

A 35-year-old woman, 5 ft 6 in and 150 lb, is moderately active. Mifflin-St Jeor gives a BMR of about 1,392 calories, and 1,392.1 × 1.55 ≈ 2,158 calories a day.

1. Protein: 2,158 × 30% = 647.4 calories, and 647.4 ÷ 4 ≈ 162 g.
2. Carbs: 2,158 × 45% = 971.1 calories, and 971.1 ÷ 4 ≈ 243 g.
3. Fat: 2,158 × 25% = 539.5 calories, and 539.5 ÷ 9 ≈ 60 g.
4. Over 3 meals, that is about 54 g protein, 81 g carbs and 20 g fat per meal.

Example 3: protein at the RDA

The same woman sets protein at 0.8 g per kg and keeps the middle preset’s 50 : 30 carbs-to-fat ratio.

1. Weight in kg: 150 × 0.45359237 ≈ 68.04 kg. Protein = 0.8 × 68.04 ≈ 54.4 g, about 54 g, which is 54.4 × 4 ≈ 217.7 calories (10.1% of 2,158).
2. Calories left: 2,158 − 217.7 = 1,940.3. Carbs get 50/80 of that, 1,212.7 calories, and fat gets 30/80, 727.6 calories.
3. Carbs = 1,212.7 ÷ 4 ≈ 303 g, and fat = 727.6 ÷ 9 ≈ 81 g.

Protein here is just above the bottom of its 10–35% range, which shows how the RDA and the AMDR are two different kinds of reference.

Macro grams at common calorie levels

All rows use the middle split of 20% protein, 50% carbs and 30% fat, rounded to the nearest gram.

Common macro calculation mistakes

• Dividing fat calories by 4. Fat has 9 calories per gram. Dividing by 4 more than doubles the fat grams.
• Percentages that do not total 100%. 30% + 30% + 30% leaves 10% of your calories unassigned. The calculator flags this.
• Using pounds in a per-kilogram rule. 0.8 g per kg is about 0.36 g per pound. Multiplying 0.8 by your weight in pounds gives more than twice the RDA.
• Expecting the grams to add back exactly. Rounding each macro to whole grams can move the total by a few calories.
• Treating a split as a diet plan. The numbers describe how calories are shared. Food choices, fiber and your health needs matter as well.

These results are estimates for healthy adults, not medical or nutrition advice. If you are pregnant, breastfeeding, under 18 or managing a condition such as kidney disease or diabetes, ask a doctor or registered dietitian what fits you.

Sources

All sources checked November 2026.

• National Academies: Rethinking the Acceptable Macronutrient Distribution Range for the 21st Century (2024), Table 3-1, AMDR values from the 2002/2005 DRI report
• National Academies (2024): Recommendations and Considerations on the future of the AMDR
• NIH NCBI Bookshelf: DRI summary table, RDAs and AIs for total water and macronutrients (protein 0.8 g/kg, carbohydrate 130 g, fiber AIs)
• HHS ODPHP: Dietary Guidelines nutritional goals by age and sex (AMDR and protein RDA)
• 21 CFR 101.9(c)(1)(i)(B): FDA general factors of 4, 4 and 9 calories per gram (Cornell LII)
• Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990 (PubMed)

Macro practice quiz: 10 questions

Test yourself with 10 multiple-choice questions. Choose an answer and press Submit to see if you are right and why. Your score appears at the end.

Frequently asked questions

How do I calculate my macros?

Start with a daily calorie target, choose what share of calories goes to protein, carbs and fat, then divide each share's calories by 4 (protein, carbs) or 9 (fat). At 1,800 calories with 20/50/30, that is 90 g protein, 225 g carbs and 60 g fat.

What is a good macro ratio?

The National Academies did not set one ratio for everyone. They set ranges for adults: 10–35% of calories from protein, 45–65% from carbohydrate and 20–35% from fat. Any split inside all three ranges fits that guidance. A dietitian can help you choose within it.

How many grams of protein do I need a day?

The adult RDA is 0.8 g per kilogram of body weight, which is 46 g a day for women and 56 g for men at the reference weights. Pregnancy and breastfeeding raise it to 71 g a day. Your own needs can differ, so check with a health professional if you have a medical condition.

Why is my fat number so much lower than carbs?

Fat has 9 calories per gram while carbs have 4. Even when fat supplies 30% of your calories, it takes fewer than half as many grams to get there.

Do my macro percentages have to add up to 100%?

Yes. Protein, carbohydrate and fat are the three calorie sources the calculator splits, so their shares must total 100% of your calories. Alcohol also has calories, but it is not part of the split.

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