TEXT HEIGHT SCALE FACTORS

PLOTTED TEXT HEIGHT PLOT SCALE 1/16" 3/32" 1/8" 5/32" 3/16" 7/72" ¼" 5/16"

DSF

FULL .0625 .09375 .125 .15625 .1875 .21875 .25 .3125 1

1/16"=1'-0" 12 18 24 30 36 42 48 60 192

3/32"=1'-0" 8 12 16 20 24 28 32 40 128

1/8"=1'-0" 6 9 12 15 18 21 24 30 96

3/16"=1'-0" 4 6 8 10 12 14 16 20 64

1/4"=1'-0" 3 4.5 6 7.5 9 10.5 12 15 48

3/8"=1'-0" 2 3 4 5 6 7 8 10 32

1/2"=1'-0" 1.5 2.25 3 3.75 4.5 5.25 6 7.5 24

3/4"=1'-0" 1 1.5 2 2.5 3 3.5 4 5 16

1"=1'-0" .75 1.125 1.5 1.875 2.25 2.655 3 3.75 12

1-1/2"=1'-0" .5 .75 1 1.25 1.5 1.75 2 2.5 8

3"=1'-0" .25 .375 .5 .625 .75 .875 1 1.25 4

1"=10' 7.5 11.25 15 18.75 22.5 26.5 30 37.5 120

1"=20' 15 22.5 30 37.5 45 52.5 60 75 240

1"=30' 22.5 33.75 45 56.25 67.5 78.75 90 112.5 360

1"=40' 30 45 60 75 90 105 120 150 480

1"=50' 37.5 56.25 75 93.75 112.5 131.25 150 187.5 600

1"=60' 45 68.5 90 112.5 135 157.5 180 225 720

1"=100' 75 112.5 150 187.5 225 262.5 300 375 1200

Drawing Scale Factor

Although recent versions of AutoCAD include tools that reduce the need for complicated scaling computations, calculating scale factors is a fact of life for CAD drafters. A useful number to know is the inverse of the plot scale, referred to as the “drawing scale factor.” The drawing scale factor can help you calculate text heights, line widths, etc., so that these items appear correctly in a plotted drawing.

It is not necessary to memorize the scale factors in the table above, because you can easily compute the Drawing Scale Factor (or DSF). For example, consider the ¼"=1'-0" plot scale. The DSF for this plot scale is 48. How is that number computed? Ask yourself a simple question:

If you can't figure it out in one step, then break it into two steps.

1) How many quarter inches are there in one inch? Hint: 4

2) How many inches are in a foot? Hint: 12

3) Multiply 4 times 12, and the result is 48, the DSF for that plot scale. (Check the table if you don't believe it.)

Note In AutoCAD, we assign a scale to a paper space viewport, so the plot scales listed above are more accurately referred to as viewport scales. The plot scale for a layout should always be 1:1, which is the scale for objects drawn in the layout.

Another way to represent the ¼"=1'-0" plot scale is as the ratio 1:48, or the fraction 1/48. Notice that if you turn 1/48 upside down (called the inverse), you get 48/1, or just 48. Therefore, we say that the DSF is the inverse of the plot scale. How can we apply this to our drawings? Suppose you want some text to be 1/8" tall in a plotted drawing. How tall must you draw it in Model space to make that happen? If your plot scale is 1/16"=1'-0", then the DSF is 192. Multiply the desired text height by the DSF to get the actual text height: 1/16 * 192 = 12. Draw the text 12" high. Plot scale and sheet size are the two factors you must consider when plotting a drawing. For instance, if your sheet size is limited to B-size (11x17), you must choose a plot scale that will allow your drawing to fit in that space. Likewise, if you do not wish to modify the plot scale, then you might need a larger sheet size to make the drawing fit.