>Why memorise this to such precision Because that was the precision used by the particular author I got it from. It's not that the fourth s.f. really matters.

>Why memorise this to such precision Because that was the precision used by the particular author I got it from. It's not that the fourth s.f. really matters. I think the 7 actually helps my memory by making the number distinctive and not just 8 1/3. It's like remembering that body temperature is 98.6 F. It's obviously false precision and it's not even an accurate average, but it's the way it's traditionally recalled - plus it works out to exactly 37 C. >8 dry ounces is approximately 8 fluid ounces I did write "cooking" originally and it is a valid point that when cooking as opposed to baking usually a little more or less liquid is immaterial. But I meant to include baking and, say, mixing drinks. A 4-5% difference isn't always important, but it's often noticeable. I've been using a digital kitchen scale for >20 years, and I just find volumetric measuring cups annoying compared to going by weight. I don't want to go back and forth filling a container and checking it on a level surface, to eyeball a meniscus, to wait for every drop of a viscous liquid to fall, or to sift flour. I don't cook or bake with liquid mercury, but I use sugar, which is ~7 ounces per cup, and flour, which is (according to me) 4.25 to 4.5 ounces per cup. That's considerably different from 8 = 8.