Hi there, Bo! While a cup of flour will be 8 ounces in terms of volume, it won't weigh a full 8 ounces (227 grams.) Think of the difference between a cup full of rocks versus a cup full of feathers. The same space is filled, but one is definitely lighter! We write our recipes using the "fluff, sprinkle, scrape" method for measuring flour (https://www.kingarthurflour.com/learn/how-to-measure-flour.html) which results in a cup weight of about 120 grams (4 1/4 ounces). This weight varies slightly between different types of flour, as shown in our Ingredient Weight Chart: https://www.kingarthurflour.com/learn/ingredient-weight-chart.html If you were to dip your measuring cup right into a bag of flour and scoop, you’d find more becomes packed in and that same cup would suddenly weigh more. There's no universal standard for what a cup of flour should weigh and we recommend copying the measurement method used by the individual who wrote the recipe you’re baking. That way you can better ensure you’re using like-kind amounts. Of course, measuring by weight (our favorite method) is even more accurate. You’ll still need to know what a recipe developer considers their cup of flour to weigh, but it’ll help you match the amount needed right down to the gram. We hope this helps clarify and happy baking! 

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