Most cells are too small to see with the naked eye. However, we can use microscopes to see the detail of very small objects, which can allow us to see what is happening inside cells.

In microscopy, ‘resolution‘ describes the ability of a microscope to distinguish detail. In other words, the shortest distance between two points that can still be distinguished as two separate entities. Different microscopes have different resolutions.

Image showing changes in resolution

Calculating the Magnification

Magnification is just the ratio of two same quantities, so it does not have any units, so it is just written with an x in front. E.g. x10 or x200

Calculating the magnification of a microscope

A compound microscope is a microscope that uses two lenses to enhance the image of a sample. The two lenses are:

  • The eyepiece lens (also known as the ocular lens)
  • An objective lens

To work out the total magnification of the light microscope, the equation is:

image showing the equation to calculate total magnification, which involves multiplying eyepiece lens magnification by the objective lens magnification

So, if the eyepiece magnification is x10 and the objective lens magnification is x60, then the total magnification is:

10 × 60 = x600

Calculating the magnification of an image

The magnification of an image can be calculated by using the equation:

Image showing the equation to calculate magnification, which involves dividing the size of the image by the real size of the image

If it is easier, you can remember the equation triangle below instead.

Triangle that shows the relationship between the size of image, the real size of image and magnification


  • Real size of image = Size of image / Magnification
  • Magnification = Size of image / Real size of image size
  • Size of image = magnification × Real size of image