hexadecimal oppacity css code example

Example 1: hex color alpha

background-color: #ffffff80; <--- 80 is 50% opacity

/*r  g  b  a*/
# ff ff ff 80;

Converted values: 
100%FF
99%FC
98%FA
97%F7
96%F5
95%F2
94%F0
93%ED
92%EB
91%E8
90%E6
89%E3
88%E0
87%DE
86%DB
85%D9
84%D6
83%D4
82%D1
81%CF
80%CC
79%C9
78%C7
77%C4
76%C2
75%BF
74%BD
73%BA
72%B8
71%B5
70%B3
69%B0
68%AD
67%AB
66%A8
65%A6
64%A3
63%A1
62%9E
61%9C
60%99
59%96
58%94
57%91
56%8F
55%8C
54%8A
53%87
52%85
51%82
50%80
49%7D
48%7A
47%78
46%75
45%73
44%70
43%6E
42%6B
41%69
40%66
39%63
38%61
37%5E
36%5C
35%59
34%57
33%54
32%52
31%4F
30%4D
29%4A
28%47
27%45
26%42
25%40
24%3D
23%3B
22%38
21%36
20%33
19%30
18%2E
17%2B
16%29
15%26
14%24
13%21
12%1F
11%1C
10%1A
9%17
8%14
7%12
6%0F
5%0D
4%0A
3%08
2%05
1%03
0%00

Example 2: background opacity css hex

background-color: #ff000088; <--- the 88 is the alpha
background-color: #ff0000 50%;