Several of my international readers have told me that they don't use kitchen scales, and while it is tempting to say, "Seriously, get some digital scales - your culinary life will be so much easier!", the following might be more immediately useful (although I still say get some scales)!
Wet and dry goods have different volumes by weight. So 100g of flour will have a different volume (which is what cups measure) than say, 100g grated cheese, or 100ml milk. By the same token, a cup of flour will weigh more than a cup of grated cheese, or 100ml milk. Make sense?
1 cup self-raising flour = 125g
1 cup grated cheddar = 113g
1 cup whole milk = 244g (or 236.89ml)
100g self-raising flour = 0.8 cup
100g grated cheddar = 0.885 cup
100ml ( (103g) whole milk = 0.422cup
Gourmet Sleuth has a is a very good converter - clicka da linka! (You may need to double-click the search results if you are using Safari or Chrome browsers. Firefox seems fine with just one click. I can't vouch for any others.)