Calculating the magnification on a compound microscope

The compound microscope uses two lenses at once: the eye-piece lens and one of the objective lenses. The magnification of the microscope is the product of the magnifying power of these two lenses. This sounds complicated but it is very easy to calculate because the magnification is written on each of the lenses.

For example: look on top of the eye-piece lens and you will probably find X10 written on it. The three objective lenses are usually: X4 (low power), X 10 (medium power) and X40 (high power).

If you have a X 10 eye-piece and you are using a X4 objective lens (low power) the total magnification will be: 10x4=X40

If you now turn to a X 10 objective lens (medium power) the total magnification will be: 10x10=X100

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