Grams tell you about mass
Grams, kilograms, ounces and pounds are weight units in everyday recipe language. A conversion from grams to ounces is the same arithmetic for flour, butter or sugar. The ingredient does not change the unit relationship.
Use a scale when a recipe calls for a weight and you have one available. Check the unit display before adding the ingredient, particularly if your scale can switch between grams and ounces.
Cups tell you about volume
Cups, spoons, millilitres and fluid ounces describe the space something occupies. A volume-to-volume conversion only needs the correct unit definitions and measurement system.
A cup of flour and a cup of honey occupy the same stated volume in the same cup system. Their weights differ. That is why a general unit chart can connect cups with tablespoons but cannot give a single gram weight for every cup.
Crossing between them needs a reference
To go from mass to volume, divide the mass by an appropriate density. For kitchen use, a published number of grams per cup offers a convenient equivalent form of that reference.
The ingredient form matters. Packing, chopping and sifting can change how much ingredient occupies the cup. Keep preparation notes with the reference and choose the closest match to the recipe. When a suitable reference is missing, the converter should ask for more information.
Do not confuse ounces with fluid ounces
The abbreviation oz normally describes mass, while fl oz describes volume. They are different quantities. A mass-to-volume conversion between them needs an ingredient reference, just as grams-to-cups does.
Always copy the full unit label with a result. If an old recipe writes only “ounces” for a liquid, check the author’s convention before entering it. A converter can calculate a chosen interpretation accurately while still giving the wrong cooking answer if the original measurement was misunderstood.