Every teaspoon is slightly different. The “standard teaspoon” (5ml) is somewhat theoretical and volume can vary massively. If you want accuracy without scales, best get a scoop like this:
They come in different sizes, measured to flat.
I’m not certain, but I think 5g of creatine is about 7.5ml, so 1 and a half scoops like that. Unless you get a 7.5ml scoop somewhere (I think Biotest superfood and creatine malate come with one, probably creatine monohydrate as well).
B.