So I am a bit lazy and I use the Norwegian metric measurements I grew up with, namely desilitres (dl), semi-interchangeably with American cup measures. If you are lucky, like me, you have a beaker or measuring cup that has both notations on it.
1 dl = 100 ml = 0,1 l.
I often make approximations of American recipes where I use 2 dl, heaped, as a rough conversion for a cup. A cup is actually about 2,4 dl or 240 ml, but it rarely seems to be a problem as long as you do it consistently with both the dry and liquid ingredients.
To be totally precise, 1 dl is 0.42 cups. Not so easy to work with. That would be about 1/3 cup plus 1.5 Tbsp, if my math is correct (given 15 ml for a Tbsp).