Enter a couple of numbers for your display, and it will tell you the width and height, and the DPI. Simple.

	Pixels wide	Pixels high
			Guess

Diagonal (" or cm)

Display name

Name	Pixels	DPI	Diagonal	Size	Pixel Count
24" wide	1920x1200	94	24.0" (61.0 cm)	20.4" x 12.7" (51.7cm x 32.3cm)	2304000	Remove
19" wide	1440x900	89	19.0" (48.3 cm)	16.1" x 10.1" (40.9cm x 25.6cm)	1296000	Remove
17"	1280x1024	96	17.0" (43.2 cm)	13.3" x 10.6" (33.7cm x 27.0cm)	1310720	Remove
20" 4:3	1600x1200	100	20.0" (50.8 cm)	16.0" x 12.0" (40.6cm x 30.5cm)	1920000	Remove
ibook	1024x768	106	12.1" (30.7 cm)	9.7" x 7.3" (24.6cm x 18.4cm)	786432	Remove