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Macro Calculator

Grams of protein, carbohydrate and fat from a calorie target and a split, with the protein checked against body weight rather than only against the percentage. A percentage split alone can leave protein too low on a small calorie target, which is where it matters most.

Also called: macros calculator, iifym calculator.

kg
%
%
Protein
158

158 g of protein, 210 g of carbohydrate and 70 g of fat on 2,100 kcal. That is 2.1 g of protein a kilogram, inside the 1.6 to 2.2 range the evidence supports for preserving lean mass. Across 4 meals that is 525 kcal and 39 g of protein each, which is a more useful target than a daily total nobody tracks in real time.

Carbohydrate
210
Fat
70
Protein a kilogram of body weight
2.1
Protein a meal
39
Calories a meal
525
Minimum fat for hormone function
38
On the protein
That is 2.1 g of protein a kilogram, inside the 1.6 to 2.2 range the evidence supports for preserving lean mass.
On the meals
Across 4 meals that is 525 kcal and 39 g of protein each, which is a more useful target than a daily total nobody tracks in real time.
How this is calculated

Where the calories come from

Total$2,100.00
Protein $630 (30%)Carbohydrate $840 (40%)Fat $630 (30%)

The split

MacroShareGramsCaloriesGrams a meal
Protein30%15863039
Carbohydrate40%21084053
Fat30%7063018
Method and background

This is what the calculation gives for the numbers you entered. It is an estimate, not advice, and it knows nothing about your situation beyond those numbers. Rules for United States change on a published schedule; the effective date is shown on every rule-based tool.

How this is calculated

Protein and carbohydrate carry four calories a gram and fat nine, so a percentage split converts directly into grams. The check that matters is protein per kilogram of body weight: the evidence supports roughly 1.6 to 2.2 grams per kilogram for preserving lean mass in a deficit, and a thirty percent share of a low calorie target can fall well below that. The page reports both and says when the percentage has left protein short. Fat has a floor too, around 0.5 grams per kilogram, below which hormone production suffers, and a very low carb split can breach it without the percentage looking unusual.

each macro share of the calories divided by its energy density: 4 kcal a gram for protein and carbohydrate, 9 for fat
s
Share of calories
k
Kcal a gram

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

a balanced split on 2100 calories

Daily calories
2,100
Weight
75 kg
Split
Balanced, 30/40/30
Custom protein share
30%
Custom carbohydrate share
40%
Meals a day
4

Protein158

2100 x 0.3 / 4

Open this example

a low calorie target leaves protein short

Daily calories
1,300
Weight
85 kg
Split
Balanced, 30/40/30
Custom protein share
30%
Custom carbohydrate share
40%
Meals a day
3

Protein98

boundary: a 30% share is well under 1.6 g/kg at this calorie level

Open this example

Method and limits

What it assumes

  • Atwater energy factors, which are averages across food types.

What it deliberately does not model

  • Fibre and alcohol are not modelled separately, though both affect the usable energy.
  • Individual response to macronutrient ratios varies, and adherence matters more than the split.

Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator

Frequently asked questions

How much protein do I actually need?
For preserving lean mass in a deficit the evidence supports roughly 1.6 to 2.2 grams per kilogram of body weight. A percentage split can undershoot that badly on a low calorie target, which is why this page checks both.
Does the exact split matter?
Less than adherence does. Hit the protein floor, keep fat above about 0.5 grams per kilogram, and the remainder is largely preference.