css的长度换算

1in = 2.54cm = 25.4 mm = 72pt = 6pc ；

• PX to EM: Example: 12px / 16px = .75em
• PX to %: Example: 12px / 16px * 100 = 75%
• PX to PT: Example: 16px * 72 (72 points = 1 inch) / 96 (96 pixels per inch in Windows, 72 in Mac) = 12pt
• EM to PX: Example: .75em * 16px = 12px
• EM to %:Example: .75em * 100 = 75%
• % to PX:Example: 75 * 16px / 100 = 12px
• % to EM:Example: 75 / 100 = .75em
• PT to PX: Example: 12pt * 96ppi / 72ppi = 16px

Pixels	EMs	Percent	Points
6px	0.375em	37.5%	5pt
7px	0.438em	43.8%	5pt
8px	0.5em	50%	6pt
9px	0.563em	56.3%	7pt
10px	0.625em	62.5%	8pt
11px	0.688em	68.8%	8pt
12px	0.75em	75%	9pt
13px	0.813em	81.3%	10pt
14px	0.875em	87.5%	11pt
15px	0.938em	93.8%	11pt
16px	1em	100%	12pt
17px	1.063em	106.3%	13pt
18px	1.125em	112.5%	14pt
19px	1.188em	118.8%	14pt
20px	1.25em	125%	15pt
21px	1.313em	131.3%	16pt
22px	1.375em	137.5%	17pt
23px	1.438em	143.8%	17pt
24px	1.5em	150%	18pt