How do you find the actual size of a biology vacuole (of a plant/animal cell)?

Basically, you use an eyepiece micrometer.

The problem with eyepiece micrometers is that they do not measure a fixed unit of measure, but must be calibrated using something of known length, like a stage micrometer. Once you know the exact conversion at the magnification of your microscope, you can measure the object.

wat do u mean by find, they r found in the cytoplasm of the cell, the difference btween them is that, the plant cell's vacule is larger since it has to store more water than the animal cell