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Nov 11, 2009 09:50 AM

Trying to convert cups of flour to ounces. Which one of these is correct ?

I've volunteered to make cupcakes for a friend's wedding this weekend. The person coordinating this gave me a recipe from Cooks Illustrated that calls for:

1 1/2 cups unbleached all-purpose flour (7 1/2 ounces)

I have to make five batches of this and wanted to find how much flour I need to buy. In using my kitchen converter calculator I noticed the amounts seems off and decided to try converting 1 1/2 cups AP flour to ounces just to verify and it gave me 6 2/3 ounces as the conversion.

So is it 7 1/2 ounces or 6 2/3 ounces? Should I just stick to measuring by cups? I normally wouldn't worry so much but since it is for a wedding I wanted to be as accurate as possible. I tried searching for the recipe but Cooks Illustrated wants my email address for a "14 day trial" and I am not falling for that.

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  1. Go with 7 1/2 ounces. One cup of flour is 5 ounces. Since I started weighing instead of measuring ingredients, I haven't had a single baking failure.

    1 Reply
    1. re: conradd

      Not necessarily. King Arthur Flour (who oughta know) use 4.25 oz. as their standard for AP flour, and of course, different types of flour (bread, whole wheat, cake, etc.) don't all weigh the same:

      I've used both 4.25 and 5 oz. as the equivalent of a cup, and I find 4.25 almost always works better.

    2. I don't understand why you must convert to cups to determine the weight of flour to buy. If you need 7.5 oz per batch, then 5 batches would be 7.5 x 5, or 37.5 oz. That's more than two, but less than 3, pounds. So that's how much flour to buy. Do be sure to use unbleached flour as the recipe recommends.

      If you'll be weighing the flour when baking, there's nothing to worry about. Use the amount the recipe specifies. If you'll be measuring with cups, there IS something to worry about. CI uses the dip-and-sweep method of measuring, and you should, too -- Dip the measuring cup into a bin of flour, then sweep across the top with a straight edge (a butter knife or icing spatula) to level the flour.

      Good luck!

      1 Reply
      1. re: Channa

        The fact that CI uses the dip-then-sweep method probably accounts for why their weight per cup is 5 ounces. Dip-then-sweep compacts flour more than spooning it into the cup then leveling. I agree with Channa that you should be sure to use the measuring method the recipe specifies.

      2. According to the book Ratio (Michael Ruhlman), a cup of flour can weigh anywhere from 4 to 6 ounces. The difference in weights is due to the amount of moisture already in the flour as well as how packed the flour is. Sift, measure and weigh and see if that helps you. If in serious doubt, just weigh ALL the ingredients and try to keep the ratio consistent.

        1. Thanks everyone! I was worried the recipe was typed incorrectly. I don't do much baking and I wanted to stick to weighing the ingrediants.