How to Use the Snellen Eye Chart

Written by maggie mccormick
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How to Use the Snellen Eye Chart
The Snellen eye chart tests your vision. (eye surgeons desk image by Keith Frith from

You've probably used the Snellen eye chart, though you may not have known its name. It's the chart that doctors use to test your vision. The Snellen chart features rows of letters with each row slightly smaller in letter size than the one above it. Doctors measure your vision by asking you to read the letters on each line, and the last line that you can read represents your "score."

Skill level:

Things you need

  • Snellen eye chart
  • Tape
  • Measuring tape

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  1. 1

    Hang the Snellen chart on the wall. It should be at eye level, meaning that the bottom of the chart should be about 60 inches off the ground.

  2. 2

    Mark the ground at 20 feet away. Measure 20 feet from the wall with the Snellen chart. Use strong tape to mark the place, as you will always stand here to take the test.

  3. 3

    Stand with your toes touching the line.

  4. 4

    Cover one eye.

  5. 5

    Read the letters on the chart. Go down each row until you cannot clearly see the letters on the row. It's helpful to have another person standing next to the chart to verify that you are saying the right letters.

  6. 6

    Calculate your vision score. There is a number next to each line on the Snellen chart. This number represents the second part of your score. So if the number on the line is 20, your score is 20/20. If the number on the line is 40, your score is 20/40. This means that you can read a letter at 20 feet that most people could read at 40 feet--and you should be wearing glasses.

  7. 7

    Repeat the eye test for the other eye.

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