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Visual Displays > Text - 3 of 9

Character and Symbol Size

Character size is one of the most important determinants of text legibility in any display, but especially with electronic displays. On computer monitors, characters are formed by small dots or pixels and are inherently less crisp and distinguishable than print on paper. Optimum character size depends on the user's position relative to the display in terms of visual angle and viewing distance.

  • Visual Angle, Viewing Distance, and Character Size Calculation - These parameters can be measured and calculated using simple algebra. Visual angle (A) is defined in degrees. The size of the visual angle depends on the size of the object being viewed (H) and its distance (D) from the observer.

  • Dynamic or Critical Display Elements
    • Characters and symbols should subtend at least 20 arcminutes.
    • Preferred is 20-22 arcminutes.
    • As a rough estimate, character size should be 1/200th of viewing distance.
  • Character/Symbol Height
    • Legibility begins to decrease with symbol heights less than 18 arcminutes.
    • Avoid symbols that subtend less than 16 arcminutes.
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