Droplets of water do not have a consistent mass because a droplet is not a regular unit of measurement. Mass can be found by depositing drops or droplets of water on a level scale and then calculating the mass in grams.
The dropper method can also be used to find the volume of a sample of water. Water deposited drop by drop in a container on a balanced scale can be evaluated in a number of valuable ways.
The number of drops used to reach given measures shows the average mass and volume of a drop when the resultant numbers are divided. Drops themselves are not consistent.