The answer depends directly on the amount of oil that you use. 1 cartridge is 2,000mg; factor in a 3% loss rate in the conversion process so you're looking at roughly 1,940mg. If you use 20ml of oil then 1,940 dvided by 20ml is 97mg per ml. Many kits come with extra so 25ml of oil woud put you closer to 77mg per ml.