How can I estimate the calories in food by weight and type. For example, if I have X ounces of meat, approximately how calories is that? Or, if I have X ounces of a starch (like a tuber) how many calories is that?

I am looking for approximate formulas, not exact amounts.


In order to know how many calories some food sample contains, you need to know exactly how much of that sample is protein, fat, and carbohydrate. This PDF from UCLA gives a breakdown of the calories per gram of those components:

  • Carbohydrate = 4 calories per gram
  • Protein = 4 calories per gram
  • Alcohol = 7 calories per gram
  • Fat = 9 calories per gram

Once you know what these are, the math is fairly straightforward; just multiply each and then add. If there are 5 grams of carbs, then totals calories from carbs equals 5 x 4 = 20; if 6 grams of protein, then 4 x 6 = 24; and so on.

Starch is a carbohydrate. But for your other example of "meat", you'd need to know the breakdown of that particular meat, so you couldn't just say X amount of meat has y amount of protein, z amount of carbohydrate, and z amount of fat. Each meat is different. That said, the breakdown of each kind of meat (i.e. chicken, lean beef, pork, etc.) is probably close enough that you could get a ballpark figure for whatever kind of meat you're interested in.

  • Very useful info, thanks very much. Is there some reason you did not upvote my question? Aug 16 '17 at 19:27
  • @TylerDurden, if you accept my answer, your rep gets increased, so I didn't see the point. However, if it makes you feel better...
    – BillDOe
    Aug 17 '17 at 19:23

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