oh and drop size is not constant. For the best accuracy make sure that your eyedropper is straight up and down (perpendicular to the ground) and drop the drops somewhat slowly.
You can also use either a slin pin or a marked dropper for very accurate measurement. I prefer this method as the drop size as was mentioned above can sometimes be inconsistent. Most drug stores sell 2 ml droppers with very accurate markings for a dollar. From there you just do the math to your dosage.
Yeah measure it. I used a slin pin then shot it back into the eyedropper and scribed the glass to get my 1ml. Or just shoot it in a cup of water with the slin pin.