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thesmu on 09/04/09


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Pixels to Ems Conversion Table for CSS


 / Published in: CSS
 

URL: http://jontangerine.com/silo/css/pixels-to-ems/

  1. Jon Tangerine / silo / CSS / Pixels to Ems Conversion Table for CSS
  2.  
  3. A companion reference to the article, The Incredible Em and Elastic Layouts With CSS.
  4.  
  5. The em values in the table assume that the generic browser default setting of 16px font size has not being changed. It also assumes that the <body> has font size set to 1em or 100%.
  6. px font-size em equivalent * Rounded to 3dp 1px in ems Notes
  7. 11 0.689 * 0.091
  8. 12 0.750 0.083
  9. 13 0.814 * 0.077
  10. 14 0.875 0.071
  11. 15 0.938 * 0.067
  12. 16 1.000 0.063 Browser standard default
  13. 17 1.064 * 0.059
  14. 18 1.125 0.056
  15. 19 1.188 * 0.053
  16. 20 1.250 0.050
  17. 21 1.313 * 0.048
  18. 22 1.375 0.046
  19. 23 1.438 * 0.044
  20. 24 1.500 0.042
  21. 25 1.563 * 0.040
  22. 26 1.625 0.039
  23. 27 1.688 * 0.037
  24. 28 1.750 0.036
  25. 29 1.813 * 0.035
  26. 30 1.875 0.033
  27. Formula to calculate em equivalent for any pixel value required
  28.  
  29. 1 ÷ parent font size (px) × required pixels = em equivalent
  30. Example: 770px wide, centred elastic layout using CSS and ems
  31.  
  32. N.B. This assumes the browser default font size is unchanged at 16px. body{} selector set to font-size:1em;. Using the forumla*:
  33.  
  34. 1 ÷ 16 × 770 = 48.125em
  35. CSS:
  36.  
  37. body{
  38. font-size:1em;
  39. text-align:center;
  40. }
  41.  
  42. div{
  43. width:48.125em;
  44. margin;0 auto;
  45. }
  46.  
  47. HTML:
  48.  
  49. <html>
  50. <body>
  51.  
  52. <div>
  53. </div>
  54.  
  55. </body>
  56. </html>
  57.  
  58. *I deliberately hooked the formula for the tutorial around 1px, as a value that designers can easily relate to. However, there is a faster way of calculating an em value that I use. You need to be familliar with the sticky issue of CSS inheritance and know the font size of the parent, but it goes like this:
  59.  
  60. Required element pixel value ÷ parent font size in pixels = em value
  61.  
  62. So, our required width of 770px in ems can be calculated like this:
  63.  
  64. 770 ÷ 16 = 48.125em
  65.  
  66.  
  67. Jon Tan fecit, 2006–2008. download vCard (via X2V).

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