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 a microscope’s ability 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.

A visual depiction of three resolution levels using pairs of blue circles. At the top, two overlapping circles with jagged edges are labelled 'Low resolution'. In the middle, two smoother overlapping circles are labelled 'Medium resolution'. At the bottom, two perfectly round and separate circles are labelled 'High resolution'.

Calculating the Magnification

Magnification is the ratio of two equivalent quantities; therefore, it does not have any units and is represented 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:

A formula to calculate magnification: Magnification is equal to the the size of image divided by real size of the image

If it’s easier, you can use the ‘equation triangle’ shown below to remember the formula.

Equation Triangle that shows the relationship between the size of image, the real size of image and magnification. The top section is labelled "Size of image", while the bottom left section is labelled "Real size of image" and the bottom right section is labelled "Magnification". The triangle is divided into these sections by two intersecting lines forming a 'T' shape within the triangle.


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

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