Hex to Octal Table – Full 0 to 255 Conversion Chart

Octal digits and their bits

Eight digits, three bits each — against hex's sixteen digits and four bits.

Octal	Binary	Decimal
0	000	0
1	001	1
2	010	2
3	011	3
4	100	4
5	101	5
6	110	6
7	111	7

Why the two never align

A hex digit is four bits and an octal digit is three. Neither divides into the other, so there is no fixed number of hex digits that maps onto a whole number of octal digits. Converting between them means going through the bits.

Where the mismatch shows

Value	Hex	Octal	Bits needed
7	7	7	3
8	8	10	4
15	F	17	4
63	3F	77	6
64	40	100	7
255	FF	377	8
511	1FF	777	9
4095	FFF	7777	12

The rows where both are neat — 63, 511, 4095 — are the ones where the bit count happens to divide by both three and four. That only occurs every twelve bits.

Full table: 00 to FF

Hex	Octal	Decimal
00	000	0
01	001	1
02	002	2
03	003	3
04	004	4
05	005	5
06	006	6
07	007	7
08	010	8
09	011	9
0A	012	10
0B	013	11
0C	014	12
0D	015	13
0E	016	14
0F	017	15
10	020	16
11	021	17
12	022	18
13	023	19
14	024	20
15	025	21
16	026	22
17	027	23
18	030	24
19	031	25
1A	032	26
1B	033	27
1C	034	28
1D	035	29
1E	036	30
1F	037	31
20	040	32
21	041	33
22	042	34
23	043	35
24	044	36
25	045	37
26	046	38
27	047	39
28	050	40
29	051	41
2A	052	42
2B	053	43
2C	054	44
2D	055	45
2E	056	46
2F	057	47
30	060	48
31	061	49
32	062	50
33	063	51
34	064	52
35	065	53
36	066	54
37	067	55
38	070	56
39	071	57
3A	072	58
3B	073	59
3C	074	60
3D	075	61
3E	076	62
3F	077	63
40	100	64
41	101	65
42	102	66
43	103	67
44	104	68
45	105	69
46	106	70
47	107	71
48	110	72
49	111	73
4A	112	74
4B	113	75
4C	114	76
4D	115	77
4E	116	78
4F	117	79
50	120	80
51	121	81
52	122	82
53	123	83
54	124	84
55	125	85
56	126	86
57	127	87
58	130	88
59	131	89
5A	132	90
5B	133	91
5C	134	92
5D	135	93
5E	136	94
5F	137	95
60	140	96
61	141	97
62	142	98
63	143	99
64	144	100
65	145	101
66	146	102
67	147	103
68	150	104
69	151	105
6A	152	106
6B	153	107
6C	154	108
6D	155	109
6E	156	110
6F	157	111
70	160	112
71	161	113
72	162	114
73	163	115
74	164	116
75	165	117
76	166	118
77	167	119
78	170	120
79	171	121
7A	172	122
7B	173	123
7C	174	124
7D	175	125
7E	176	126
7F	177	127
80	200	128
81	201	129
82	202	130
83	203	131
84	204	132
85	205	133
86	206	134
87	207	135
88	210	136
89	211	137
8A	212	138
8B	213	139
8C	214	140
8D	215	141
8E	216	142
8F	217	143
90	220	144
91	221	145
92	222	146
93	223	147
94	224	148
95	225	149
96	226	150
97	227	151
98	230	152
99	231	153
9A	232	154
9B	233	155
9C	234	156
9D	235	157
9E	236	158
9F	237	159
A0	240	160
A1	241	161
A2	242	162
A3	243	163
A4	244	164
A5	245	165
A6	246	166
A7	247	167
A8	250	168
A9	251	169
AA	252	170
AB	253	171
AC	254	172
AD	255	173
AE	256	174
AF	257	175
B0	260	176
B1	261	177
B2	262	178
B3	263	179
B4	264	180
B5	265	181
B6	266	182
B7	267	183
B8	270	184
B9	271	185
BA	272	186
BB	273	187
BC	274	188
BD	275	189
BE	276	190
BF	277	191
C0	300	192
C1	301	193
C2	302	194
C3	303	195
C4	304	196
C5	305	197
C6	306	198
C7	307	199
C8	310	200
C9	311	201
CA	312	202
CB	313	203
CC	314	204
CD	315	205
CE	316	206
CF	317	207
D0	320	208
D1	321	209
D2	322	210
D3	323	211
D4	324	212
D5	325	213
D6	326	214
D7	327	215
D8	330	216
D9	331	217
DA	332	218
DB	333	219
DC	334	220
DD	335	221
DE	336	222
DF	337	223
E0	340	224
E1	341	225
E2	342	226
E3	343	227
E4	344	228
E5	345	229
E6	346	230
E7	347	231
E8	350	232
E9	351	233
EA	352	234
EB	353	235
EC	354	236
ED	355	237
EE	356	238
EF	357	239
F0	360	240
F1	361	241
F2	362	242
F3	363	243
F4	364	244
F5	365	245
F6	366	246
F7	367	247
F8	370	248
F9	371	249
FA	372	250
FB	373	251
FC	374	252
FD	375	253
FE	376	254
FF	377	255

Unix permission modes

This is where most people actually meet octal, and it is a good illustration of when three-bit grouping is the right choice.

Octal	Bits	Permissions	Hex
0	000	none	0
1	001	execute	1
2	010	write	2
4	100	read	4
5	101	read, execute	5
6	110	read, write	6
7	111	read, write, execute	7

chmod 755

  7 = 111  owner:  read, write, execute
  5 = 101  group:  read,        execute
  5 = 101  others: read,        execute

  the same value in hex: 1ED

755 shows three permission triples at a glance. 1ED is the same number and shows nothing. Where the underlying fields are three bits wide, octal genuinely is the better notation — which is why it survives there and almost nowhere else.

Converting between them

Go through binary in both directions. Expand to bits, then regroup: fours for hex, threes for octal, always counting from the right. The hex to octal converter and octal to hex converter do this for values of any length.

Frequently asked questions

What is FF in octal?

377. Both represent 255 in decimal.

Why does octal have no 8 or 9?

Base 8 uses only digits 0 to 7. Eight rolls over to 10 in octal, the same way ten rolls over to 10 in decimal.

How do I convert hex to octal?

Expand each hex digit to four bits, join them, then regroup the bit string into threes from the right.

Why is there no direct digit mapping?

A hex digit is four bits and an octal digit is three. Neither divides into the other, so the digits never line up.

What is chmod 755 in hex?

1ED. But hex is the wrong notation for permissions, because the fields are three bits wide.

Is octal still used?

Mainly in Unix file permissions. It was common on older machines with word sizes divisible by three, before eight-bit bytes made hex the better fit.

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