Selecting "Edit > Preferences Dialog > System." lets you set the unit system, with choices:
- units (u)
- pixels (px)
- points (pt)
- inches (in)
- metres (m)
- centimeters (cm)
- millimeters (mm)
The conversions are:
- 1cm = 0.01m = 10mm
- 1in = 2.54cm
- 1in = 72pt
- 1u = (image width in pixels)/(image area width)px
- 1in = (res)px
The default document is 480 x 270 pixels and has an image area from (-4,2.25) to (4,-2.25), giving an image area of 8 x 4.5 units, so by default 1 unit is 480 / 8 = 60 pixels.
At an XRes = YRes = 36, 1in = 72pt = 36px = 0.6u.
At an XRes = YRes = 72, 1in = 72pt = 72px = 1.2u.
Another example, linking all 7 units:
72 DPI: (1m = 100cm = 1000mm = 39.37in = 2834.65pt) = (2834.65px = 47.24u) 36 DPI: (1m = 100cm = 1000mm = 39.37in = 2834.65pt) = (1417.32px = 23.62u)