4ml per 100ml of juice made... so 1500ml will make you 37.5 liters of juice.... 1500/4=375 100ml bottles or 37.5 liters (9.9gal) of juice
If you vape 30ml/week, that will keep you vaping for 1250 weeks, or 24 years, lol... 50ml/week is 750 weeks, or just shy of 14.5 years....
I just did the same math on my stockpile of Nicotine I have enough to make 25L, and will be ordering another batch soon, so I can have enough to keep me and my SO in juice through 100L (25+ gal).... which should hopefully outlast these insane regulations, or until we give up the need for Nicotine?