Several people have asked how I know what the cost per serving is for different items.
My main source for information is the USDA database called The Nutritional Composition Of Foods. For years I owned the paperback versions that they printed in the 70s and 80s. Fortunately the information is now available online. I use other USDA publications as well, including a pamphlet I picked up when my kids were little that lets you calculate how much food to buy for day-care centers that serve meals. Now I use it to help my sons to figure out how much food to buy for their growing families.
Over the years, I've created a spreadsheet that does all the arithmetic for me. All I have to do is type in the price per pound, and the number of servings and it tells me how much to buy and how much it will cost. This week I spent a bit of time working on the spreadsheet to create some Magic Numbers for folks who read this blog.
The Magic Number for a food item is used two ways.
1) Multiply the Magic Number by the price per pound. That will give you the cost of a 1 ounce serving of cooked meat.
2) Multiply the number of servings by the size of the serving in ounces. Then multiply that by the Magic Number. That will tell you how much raw meat to buy.
Magic Numbers for fruits and vegetables work in a similar way. You'll get a different number of servings from a pound of fresh green beans than you will from frozen. And you'll get a different number of servings from a 1 pound can of green beans than you will from a 1 pound bag of frozen green beans. The Magic Number times the price per pound will give you the cost of a 1/2 C serving of that fruit or vegetable. The Magic Number times the number of servings will give you the amount you need to purchase.
When I post the price per serving each week, I take all these differences into account. That's how I come up with the comparisons between the various sale prices in the ads.
For those of you who want more details:
Let's try an example. The Magic Number for chicken thighs is .1202.
If chicken thighs are 99 cents per pound, you multiply .1202 times .99. That gives you .119. Read that as the dollars per serving, ie $0.119, or roughly 12 cents per 1 oz serving. (Only look at the first 2 or 3 numbers to the right of the decimal point. The rest is just junk).
If you need to serve 4 people, and you want each of them to have a 4 ounce serving of meat, you first multiply 4 times 4, or 16. Then you multiply the Magic Number by 16. 16 x .1202 = 1.92. Read that as 1.9 pounds of chicken thighs. If you want to serve 4 people 4 ounces of cooked meat, then you'll need to buy about 2 pounds of chicken thighs. If you only want to serve 3 ounces per person, then you'll only need 12 x .1202, or 1.4 pounds of chicken thighs.
If people want this information, I will start including it in my posts. Let me know by leaving a comment below.