How does Chronometer calculate protein %age for individual foods?

I decided to calculate the protein %age for broccoli, and the data I got from the USDA does match the data in Chronometer’s USDA broccoli entry. But I calculated 29% protein while Chronometer calculates 20% protein. 

My method was to start with the (rounded) data: 

2.82g protein

0.37g fat

6.64g carbs

Then I took the protein and divided it by sum of all 3 macros. Then multiply by 100 to get the percentage.


Is this approach correct? How does Chronometer do it?

I’m using broccoli as a generic example and assuming I will run into similar variation in other foods. I’m considering increasing my protein intake from 10-15% to 20-25%, so I’m a little concerned that I don’t understand why my calculations are 9% off of Chronometer’s despite using the same data.

Thanks for the help!


  • Update: Seems like this calculation is meant to be done in Calories, not grams. Still the protein %age doesn’t match the USDA’s (20%) though:

    2.82 g x 4 Cal/g = 11.28 Cal protein

    0.37 g x 9 Cal/g = 3.33 Cal fat

    6.64 g x 4 Cal/g = 26.56 Cal carbohydrates

    (11.28/(11.28+3.33+26.56)) * 100 = 27%

    This raises another question. The sum of the calories of each macro (41.17 Cal) is greater than the total Calories recorded by the USDA (34 Cal). How is this possible? I heard something about some kinds of fiber in carbs not always being counted towards total calories. I wonder if that explains it or I’m still missing something...

  • edited December 2021

    Hi Rosy,

    On average, protein gives us 4 kcal/g, however there are more precise energy factors used for different foods that we can use when they are available. For a food like broccoli, we are not able to digest all the protein so the energy factor is quite a bit lower, at 2.44 kcal/g

    The data comes from Food Data Central:
    Hover your mouse over the calculated energy value and you can see the energy factor for each of the macronutrients to see how they energy in this food was calculated.

    Karen Stark
    As always, any and all postings here are covered by our T&Cs:

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