Just figure out roughly how many drops from dropper there are per ml and do the math. Its not gunna be exact but you can get close enough. For example, I have some liquid finasteride thats 5mg/ml and there are roughly 30 drops from the dropper per ml. If I want to take 0.5 mg I would take 3 drops. (5/30 = 0.166667 ===> 0.166667*3 = 0.5)