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macronutrient distribution

How macronutrient distribution works

A calorie target alone says nothing about protein, carbohydrate or fat: the AMDR range defines, by age group, how much of each macronutrient fits inside that total, and this page walks through the math that turns a percentage into grams.

Three ranges by age, one gram calculation

The AMDR (Acceptable Macronutrient Distribution Range) is the Institute of Medicine reference band for the share of calories that comes from each macronutrient. It changes by age group: children ages 1 to 3 sit between 5% and 20% protein and 30% to 40% fat; ages 4 to 18, protein rises to 10% to 30% and fat drops to 25% to 35%; in adults, protein runs 10% to 35% and fat 20% to 35%. Carbohydrate is the only one that stays fixed: 45% to 65% across all three age groups.
To become grams, each percentage runs through the Atwater factors: protein and carbohydrate are worth 4 kcal per gram, fat is worth 9 kcal per gram, more than double. On a 2000 kcal diet with percentages set at the midpoint of each range (22.5% protein, 55% carbohydrate, 27.5% fat), the math lands on 113 g of protein, 275 g of carbohydrate and 61 g of fat, each value rounded to the nearest whole gram.
The real trap is the typed percentage, not the formula: asking for 50% protein on a 2000 kcal adult diet does not return half the calories as protein. The calculation clamps the value to the adult AMDR ceiling, 35%, and returns 175 g, not the 250 g that 50% would produce. The same happens at the floor: asking for 40% carbohydrate inside a range whose minimum is 45% silently pushes the value back up to 45%.

Three distributions calculated end to end

Adult, 2000 kcal, default percentages

Input: 2000 kcal, 30 anos, sem percentual informado
Expected output: Proteína 113 g (22,5%), carboidrato 275 g (55%), gordura 61 g (27,5%)

With no percentage chosen, the calculation uses the midpoint of each adult AMDR range (protein 10 to 35%, carbohydrate 45 to 65%, fat 20 to 35%), so the result always lands at the center, never at an edge.

Adult, 2500 kcal, high protein and below-floor carbohydrate

Input: 2500 kcal, 35 anos, proteína 35%, carboidrato 40%, gordura 25%
Expected output: Proteína 219 g (35%), carboidrato 281 g (45%, não 40%), gordura 69 g (25%)

The requested protein, 35%, is already the range ceiling and passes through unchanged; the requested carbohydrate, 40%, falls below the 45% floor and gets raised to it, so the gram result reflects 45%, not the 40% typed in.

Fifteen-year-old, 1600 kcal

Input: 1600 kcal, 15 anos
Expected output: Proteína 80 g (20%), carboidrato 220 g (55%), gordura 53 g (30%)

At age 15 the calculation uses the 4-to-18 range, with a 30% protein ceiling instead of the adult 35% and a 35% fat ceiling; the age-group difference changes the result even at the same total calories.

Full tool FAQ

Does it build a diet?

No. It converts percentages to grams and shows population ranges.

What is AMDR?

Is higher protein always better?

Are carbohydrates required?

Does fat have more calories?

Can children use it?

What about fiber?

Should percentages sum to 100?

Can I use it for bulking/cutting?

Is data saved?

Frequently asked questions

What is the difference between the AMDR range and the daily protein recommendation?

They operate on different scales. The daily protein recommendation (RDA) is a fixed floor in grams per kilogram of body weight, 0.8 g/kg/day for adults, independent of total calories. The AMDR is a percentage range of total calories (10% to 35% in adults) used to plan the split between the three macronutrients, not a safety minimum.

Why is the carbohydrate range the same for children and adults?

Because within the AMDR, only the protein and fat ranges change by age; carbohydrate stays fixed at 45% to 65% of total calories across the three defined age groups (1 to 3 years, 4 to 18 years and adults), so changing age does not shift that particular interval.

What do the 4 kcal and 9 kcal per gram figures for each macronutrient mean?

These are the Atwater factors, used to convert grams into calories: 1 g of protein or carbohydrate is worth 4 kcal, and 1 g of fat is worth 9 kcal. That is why the same percentage slice of calories yields fewer grams of fat than of protein or carbohydrate.

Can I type in any protein percentage I want?

You can type any number, but the calculation only accepts values inside your age group AMDR range; a percentage above the ceiling or below the floor is automatically pulled to the nearest edge before it turns into grams, with no visible warning that an adjustment happened.

Next steps

Macro	Selected	AMDR range
Protein	110 g · 20%	10–35% · 55–193 g
Carbohydrates	275 g · 50%	45–65% · 248–358 g
Fat	73 g · 30%	20–35% · 49–86 g

Macro

Selected

AMDR range

Protein

110 g · 20%

10–35% · 55–193 g

Carbohydrates

275 g · 50%

45–65% · 248–358 g

Fat

73 g · 30%

20–35% · 49–86 g

Continue in the tool

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macronutrient distribution

How macronutrient distribution works

Three ranges by age, one gram calculation

The AMDR (Acceptable Macronutrient Distribution Range) is the Institute of Medicine reference band for the share of calories that comes from each macronutrient. It changes by age group: children ages 1 to 3 sit between 5% and 20% protein and 30% to 40% fat; ages 4 to 18, protein rises to 10% to 30% and fat drops to 25% to 35%; in adults, protein runs 10% to 35% and fat 20% to 35%. Carbohydrate is the only one that stays fixed: 45% to 65% across all three age groups.

To become grams, each percentage runs through the Atwater factors: protein and carbohydrate are worth 4 kcal per gram, fat is worth 9 kcal per gram, more than double. On a 2000 kcal diet with percentages set at the midpoint of each range (22.5% protein, 55% carbohydrate, 27.5% fat), the math lands on 113 g of protein, 275 g of carbohydrate and 61 g of fat, each value rounded to the nearest whole gram.

The real trap is the typed percentage, not the formula: asking for 50% protein on a 2000 kcal adult diet does not return half the calories as protein. The calculation clamps the value to the adult AMDR ceiling, 35%, and returns 175 g, not the 250 g that 50% would produce. The same happens at the floor: asking for 40% carbohydrate inside a range whose minimum is 45% silently pushes the value back up to 45%.

Three distributions calculated end to end

Adult, 2000 kcal, default percentages

Input: 2000 kcal, 30 anos, sem percentual informado
Expected output: Proteína 113 g (22,5%), carboidrato 275 g (55%), gordura 61 g (27,5%)

Adult, 2500 kcal, high protein and below-floor carbohydrate

Input: 2500 kcal, 35 anos, proteína 35%, carboidrato 40%, gordura 25%
Expected output: Proteína 219 g (35%), carboidrato 281 g (45%, não 40%), gordura 69 g (25%)

Fifteen-year-old, 1600 kcal

Input: 1600 kcal, 15 anos
Expected output: Proteína 80 g (20%), carboidrato 220 g (55%), gordura 53 g (30%)

Full tool FAQ

Does it build a diet?

No. It converts percentages to grams and shows population ranges.

What is AMDR?

Is higher protein always better?

Are carbohydrates required?

Does fat have more calories?

Can children use it?

What about fiber?

Should percentages sum to 100?

Can I use it for bulking/cutting?

Is data saved?

Frequently asked questions