The total magnification of “40x” is usually 400x on a standard compound microscope, assuming a 10x eyepiece.

Quick Scoop

  • Total magnification formula : objective lens magnification × eyepiece magnification.
  • In most school or lab microscopes, the eyepiece is 10x.
  • So if you are using the 40x objective , total magnification = 40 × 10 = 400x.
  • Some people casually say “40x microscope” to mean “40 times larger,” but in teaching contexts “40x objective” almost always means 400x total with a 10x eyepiece.

Mini Example

If your microscope has objectives 4x, 10x, and 40x and an eyepiece of 10x:

  1. 4x objective → 4 × 10 = 40x total
  2. 10x objective → 10 × 10 = 100x total
  3. 40x objective → 40 × 10 = 400x total

So when someone in class asks “what is the total magnification of 40x?”, the expected answer is 400x , unless your eyepiece is something other than 10x.

TL;DR: With a typical 10x eyepiece, 40x on the objective gives a total magnification of 400x.

Information gathered from public forums or data available on the internet and portrayed here.