I usually squeeze about 12oz of juice per drink into a 16 oz glass. I hope this helps. I'm not a mixologist, I don't play one on the internet and I've never measured a drink in my life (I do say 'about'). Everyone wants their drinks mixed to taste so experiment and enjoy.
I'm also lucky enough to have a mint plant by my back door, so I garnish with fresh mint, when I remember it.