A cup of flour and a cup of honey weigh nothing like each other, so pick the ingredient and this converts by weight properly. Background in cooking conversions.
Weights are grams per US cup (240ml) and are practical averages; how you scoop and pack, humidity and brand all shift flour and sugar by a few per cent, so for baking that matters, weigh rather than trust any cup figure. Ounces here are weight ounces (28.35g), not fluid ounces. A UK/metric cup is 250ml rather than 240; the difference is about 4 per cent.
How many grams is a cup of flour?
About 125 grams for plain or all-purpose flour, though it shifts a few per cent with how you scoop. For anything where the ratio matters, weigh it.
Why does a cup of flour weigh differently from a cup of sugar?
A cup is a volume, not a weight, so every ingredient fills it at a different density. That is why this tool asks which ingredient before it converts.
Where can I read more?
The full ingredient-by-ingredient background is in the cooking conversions reference.