Actually no, it does not work that way. Ounces of weight are not the same as ounces of volume.
I think originally a liquid ounce was defined as the volume of an ounce weight of water. It is close to that, but not exact. And since sugar does not weigh the same as water you couldn't use that for the conversion.
According to the rec.cooking.faq, granulated sugar weighs 190 grams per cup.
Each material has a different density, so you need to consult a site which has worked this all out for you.
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for sugar, and there is a similar one for flour.
BTW, why do y'all measure solids using volume, whilst the rest of us around the world use weight?
Using volume, you always must sift the sugar/flour first, then measure it. Using weight you can measure out what you need and then just sift that.
C'mon America, get with it!