1 mil is exactly 1 x 10-3 inches. In SI units 1 mil is 2.54 x 10-5 meters.
1 Twip is exactly one twentieth (1/20) of a PostScript point. A PostScript point itself being 1/72 of an inch, making a twip 1/1440 inch. 1 Twip is approximately 1.763889 x 10-5 meters (SI base unit). 1 twp ≈ 0.000017638888888889 m.