Macro Calculator
Convert a daily calorie figure into grams of protein, carbohydrate and fat, and check the split against the published AMDR bands.
Result
Enter daily calories to see the result.
https://calcgallery.com/nutrition-energy/macro-calculator/
How to use the Macro Calculator
- Enter the daily calorie figure you are working to.
- Choose the AMDR midpoint preset, or set your own three shares.
- If you choose your own, make the three add up to 100%.
- Read the grams, and check whether your split sits inside the published bands.
How it is calculated
Each macronutrient carries a known amount of energy per gram, so a share of a calorie figure converts straight into grams:
protein g = calories × protein share ÷ 4carbohydrate g = calories × carbohydrate share ÷ 4fat g = calories × fat share ÷ 9Those divisors are the general Atwater factors from USDA Agriculture Handbook 74. They are the energy the body extracts rather than the energy released by burning the food in a laboratory, which is why protein is 4 rather than about 5.
The Institute of Medicine publishes acceptable macronutrient distribution ranges for adults:
| Macronutrient | AMDR | Midpoint |
|---|---|---|
| Protein | 10 to 35% of energy | 22.5% |
| Carbohydrate | 45 to 65% of energy | 55% |
| Fat | 20 to 35% of energy | 27.5% |
Those three midpoints add up to 105%, so the preset on this page cannot use all three. Protein and fat sit at their midpoints and carbohydrate takes the remainder, which lands at 50% — comfortably inside its own band. That choice is stated here rather than made quietly, because the preset has to resolve the arithmetic somehow.
The shares must total 100%. A custom split that does not is rejected with a message naming the total it got. The alternative, silently scaling the three shares until they fit, returns grams for a split you did not enter.
This page does not recommend a split. It converts the one you choose and tells you whether each share falls inside the IOM range. Falling outside a band is a note, not a verdict: the bands describe what the IOM considered acceptable for the general adult population, and plenty of deliberate dietary patterns sit outside them.
No named diet presets ship here. Keto, zone and the rest are defined differently by different sources, and none of those definitions could be traced to a citable original. An uncited preset would be an invented number wearing the costume of a standard.
Practical tips
Protein is the share worth setting first. It is the one with the strongest evidence behind a deliberate choice, and once it is fixed the other two are dividing what remains.
The fat share always looks small in grams. Nine kilocalories a gram means a 30% fat share produces about a third of the grams the same carbohydrate share would. That is arithmetic, not an error.
Round sensibly when you apply it. These figures are computed to the gram, but food labels, portion sizes and your own consistency are nowhere near that precise. Whole tens of grams is a realistic working precision.
A split outside a band is not a problem to fix. It is information. The bands are wide precisely because a wide spread of splits supports adequate nutrition.
Check the calorie figure first. Everything on this page scales linearly with it, so an inaccurate maintenance estimate makes every gram figure wrong by the same proportion.
With your numbers
- Fat carries 9 kcal a gram, so its share gives 67 g
- Carbohydrate at 4 kcal a gram gives 275 g
- Protein at 4 kcal a gram: 2,200 kcal × its share ÷ 4 = 124 g (2,200 kcal split three ways)
Quick reference
This page does not recommend a split. It converts the one you choose and says whether it sits inside a published band.
| Example | Protein |
|---|---|
| 1,600 kcal, AMDR midpoints | 90 g |
| 1,800 kcal, AMDR midpoints | 101 g |
| 2,000 kcal, AMDR midpoints | 112 g |
| 2,200 kcal, AMDR midpoints | 124 g |
| 2,500 kcal, AMDR midpoints | 141 g |
| 2,000 kcal at 25/45/30 | 125 g |
| 1,600 kcal at 30/40/30 | 120 g |
| 3,000 kcal, AMDR midpoints | 169 g |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
2 sources
Merrill AL, Watt BK, Energy Value of Foods: Basis and Derivation, USDA Agriculture Handbook No. 74 (slightly revised February 1973), p. 48, the "general factors 4, 9, 4", https://www.ars.usda.gov/ARSUserFiles/80400525/Data/Classics/ah74.pdf
Used for
- General Atwater energy factor for protein.
- General Atwater energy factor for carbohydrate.
- General Atwater energy factor for fat.
Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2002/2005), Summary Tables, p. 1325, Acceptable Macronutrient Distribution Ranges, adults: protein 10-35, carbohydrate 45-65, fat 20-35 percent of energy. https://nap.nationalacademies.org/read/10490/chapter/32
Used for
- Lower protein AMDR for adults.
- Upper protein AMDR for adults.
- Lower carbohydrate AMDR for adults.
- Upper carbohydrate AMDR for adults.
- Lower fat AMDR for adults.
- Upper fat AMDR for adults.
Common questions about the Macro Calculator
- What split should I use?
- This page does not answer that. The Institute of Medicine publishes acceptable ranges rather than a recommended point, which is itself an answer: a wide spread of splits is compatible with adequate nutrition for healthy adults. The preset here sits at the middle of those ranges because a midpoint is a defensible default, not because it is optimal for anyone in particular.
- Why does protein have 4 calories per gram?
- The Atwater general factors of 4, 4 and 9 kilocalories per gram come from USDA Agriculture Handbook 74 and reflect the energy the body actually extracts, after losses in digestion and in urea excretion. Protein and carbohydrate release similar amounts; fat is a more reduced molecule and releases more than twice as much per gram, which is why a fat share always produces fewer grams than the same carbohydrate share.
- Do the AMDR bands apply to athletes?
- They were set for the general healthy adult population, and the IOM did not derive them for athletic performance. Sports nutrition bodies publish their own protein ranges that sit above the AMDR midpoint, which is a different question from adequacy. This page reports whether a split is inside the IOM bands and does not claim those bands are the right target for training.
- Does alcohol count?
- It carries about 7 kilocalories per gram and is not modelled here. The IOM does not include it in the AMDR because it is not a required nutrient, so a split of protein, carbohydrate and fat that totals 100% implicitly assumes no alcohol. If a meaningful part of your intake is alcohol, the grams this page produces will overstate what is left for the three macronutrients.
- Why does it reject my split instead of fixing it?
- Because normalising a 97% split up to 100% produces grams for a split you did not choose, and you would have no way of reconciling the output with what you typed. The calculator says which total it got and which field to change. That takes one more moment and never returns a number under false pretences.