I make this for my kids in the summer and I think it's about 1/5 coffee to water by volume not weight. It comes out so smooth and strong. Closer to an espresso in strength, good undiluted but better diluted.
I sub it for espresso in cold drinks - there is this weird one supposed to be made with fresh orange juice, espresso and fizzy water, recipe had a lot of advice about not shocking the espresso but it's so much easier and better with cold brew. Cocktails too. Shaken with ice, delicious.