Magnification Formula

Magnification = Image size ÷ Actual size

Magnification equation

Rearranging the equation to find things other than the magnification becomes easy when you remember the triangle - whatever you are trying to find, place your finger over it and whatever is left is what you do, so:
- Magnification = image size / actual size
- Actual size = image size / magnification
- Image size = magnification x actual size

Remember magnification does not have any units and is just written as ‘x 10’ or ‘x 5000’

An image of an animal cell is 30 mm in size and it has been magnified by a factor of x 3000. What is the actual size of the cell?

To find the actual size of the cell:

Worked Example Using Magnification Equation

Worked example using the magnification equation

To ensure you do not lose marks when answering exam questions on this skill:

Always look at the units that have been given in the question - if you are asked to measure something, most often you will be expected to measure it in millimetres NOT in centimetres - double check the question to see! Remember to bring a ruler to the exam!
Learn the equation triangle for magnification and write it on the page straight away
Don’t forget that magnification has NO UNITS - students often lose a mark because they put one in

Magnification Formula (Cambridge O Level Biology)