How much does 1 C of all purpose flour weigh?
Tue, 03/31/2009 - 23:46
This is a really newbie question but I've always thought 1 C of AP flour is 5 oz. but after some Googling some sites say 4.4something ounces and now I'm just confused! I should probably get this straightened out before I start baking for my friend's wedding! 
Thanks for the help DBs.
I went to www.onlineconversion.com and they say that all purpose flour with a density of o.42 g/ml is ~3.5 ounces. I encourage you to use this site for all of your conversions. They are very accurate.
Your scale should be acurate too. Calibrate it with known weights.
HTH
How much does a cup of AP flour weigh is a question that depends on many factors.
Firstly the cup is a different size across the world
In Australia, Canada, New Zealand one cup is defined as 250 millilitres. This is the commonly used cup.
1 metric cup = 250 millilitres
= 16⅔ international tablespoons (15ml=1 International tablespoon)
= 12½ Australian tablespoons (20ml=1 Australian tablespoon)
≈ 8.7988 imperial fluid ounces
≈ 8.4535 U.S. customary fluid ounces
United States customary cup is defined as half a U.S. pint.
1 U.S. customary cup = 0.5 U.S. customary pints
= 2 U.S. customary gills
= 8 U.S. customary fluid ounces
= 16 U.S. customary tablespoons
= 236.5882365 millilitres ≈ 237 ml
≈ 15⅔ international tablespoons
≈ 11¾ Australian tablespoons
≈ 0.8327 imperial cups
≈ 8.3267 imperial fluid ounces
United States "legal" cup
The cup currently used in the United States for nutrition labelling is defined in United States law as 240 ml.
1 U.S. "legal" cup = 240 millilitres
= 16 international tablespoons
= 12 Australian tablespoons
≈ 8.1154 U.S. customary fluid ounces
≈ 8.4468 imperial fluid ounces
The Japanese cup is currently defined as 200 ml.
1 Japanese cup = 200 millilitres
≈ 7.0390 imperial fluid ounces
≈ 6.7628 U.S. customary fluid ounces
So a cup of flour weighs a different amount in different countries and since different flours have different densities (.4-.6 g/ml) the best you can give is a range of values. (White wheat flour has an average density of roughly .55 g/ml)
US Light All Purpose Flour (density of .42 g/ml)
1 metric cup = 105 grams = 3.7 ounces
1 US customary cup = 99 grams = 3.5 ounces
1 Japanese cup = 84 grams = 3 ounces
US White Wheat All Purpose flour (density of .5 g/ml)
1 metric cup = 125 grams = 4.4 ounces
1 US customary cup = 120 grams = 4.2 ounces
1 Japanese cup = 100 grams = 3.5 ounces
Average White Wheat flour (density of .55 g/ml)
1 metric cup = 138 grams = 4.9 ounces
1 US customary cup = 130 grams = 4.6 ounces
1 Japanese cup = 110 grams = 3.9 ounces
Australian Plain flour (density of .6 g/ml)
1 metric cup = 150 grams = 5.3 ounces (standard in Australian cookbooks)
1 US customary cup = 142 grams = 5 ounces
1 Japanese cup = 120 grams = 4.2 ounces
I would in your case use US White Wheat All Purpose flour
1 US customary cup = 120 grams = 4.2 ounces
Don't be surprised if different cookbook say different amounts, always go by the feel of the recipe and the final purpose. I always touch and taste batters and doughs so I know if I'm using the right amount of flour.
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I think it really depends on the recipe. For some recipes one cup can equal more flour than others and it really depends on the proportion of the other ingredients. Cook's illustrated uses 5 oz for one cup of all purpose flour, so for their recipes you would have to use 5 oz to represent one cup.
Thanks for the help so far. The reason why I asked was because I saw that CI uses 5oz. and that's why I've been using 5oz. but some online sources have different values.
This thread really helps to illustrate why weighing ingredients all the time is so much better than using volume measurements!! If I scoop my flour into the cup, it's 140 grams. If I spoon it in, it's 135 grams. If I shake the cup to even the top, it's 145-150 grams. . . . you might want to seek out recipes that use weights to begin with, and just follow those! (PS--here in Canada, it's true, we're told a "cup" is 250 ml., but I've never seen a measuring cup where one cup actually pours out to 250 ml. . . they're all made in the US, I guess, so a liquid cup is actually 240 ml., in my experience).
I've been using 5 oz for 1 cup too.. then I noticed that King Arthur uses less. For their yellow butter cake, there were a lot of bad reviews.. I have a feeling ti's because people didn't look at the weighted measurements and went with the cup. King Arthur uses way less than 5 oz for 1 cup. I find that when I measure flour by spooning it in and then giving it a little shake when halfway full then spooning in the rest, it usually comes to 5 oz. Since most of the recipes I bake are CI anyway, I guess 5oz for 1 cup is good for me.
Flour weight depends entire on the packing of the flour, the amount you've sifted, the amount you've been able to shove into said cup... I find weight is MUCH more accurate for measuring dry ingredients than cups. School won't even let me use cups at all, because it greatly effects the outcome. 250g of flour is simply that. 1 cup can be 100-300 grams depending on so many factors! That's a lot of leeway!
-Elizabeth