Chris I hope I understand your question correctly so here goes it.
Typically the dose is put on the label such as 200mcg/ml or 4mg/ml.
Say u wanted a dose of 40mcg. To find that we would take 40/200 = 1/5 or .2ml.
I prefer using a syring bc some dosages such as .2ml are not labeled on the dropper. usually the dropper is 1ml and it will have at least 4 dashes on it making 1ml, .75ml, .5ml. & .25ml.
Hope this helps!