Binary Conversion Chart (0–255)

Q: How many hex digits make a byte?

Two. Each hex digit represents exactly four bits, so FF is 11111111, which is 255.

Q: What is 0xFF in decimal?

255. The 0x prefix marks hexadecimal, and FF is 15×16 + 15.

Every value a byte can hold, shown in binary, decimal, hexadecimal and octal side by side — with the ASCII character, powers of two and the boundary values that cause bugs.

Updated: 2 August 2026Read: 7 minRuns: 100% in your browser

How to use this chart

Every row shows the same value in five notations. Reading across converts between them instantly — no arithmetic required.

The relationships are fixed and worth internalising:

4 bits = 1 hex digit. Split any binary byte into two nibbles and convert each separately: 1101 0110 is D6.
3 bits = 1 octal digit. Group from the right: 11 010 110 is 0o326.
8 bits = 1 byte, covering 0–255 unsigned or −128–127 signed.

Filter

0 to 255 in four bases

Every value a single byte can hold, with the corresponding ASCII character where one exists.

0–63

Decimal	Binary	Hex	Octal	ASCII
0	00000000	0x00	0o000	`NUL`
1	00000001	0x01	0o001	`SOH`
2	00000010	0x02	0o002	`STX`
3	00000011	0x03	0o003	`ETX`
4	00000100	0x04	0o004	`EOT`
5	00000101	0x05	0o005	`ENQ`
6	00000110	0x06	0o006	`ACK`
7	00000111	0x07	0o007	`BEL`
8	00001000	0x08	0o010	`BS`
9	00001001	0x09	0o011	`HT`
10	00001010	0x0A	0o012	`LF`
11	00001011	0x0B	0o013	`VT`
12	00001100	0x0C	0o014	`FF`
13	00001101	0x0D	0o015	`CR`
14	00001110	0x0E	0o016	`SO`
15	00001111	0x0F	0o017	`SI`
16	00010000	0x10	0o020	`DLE`
17	00010001	0x11	0o021	`DC1`
18	00010010	0x12	0o022	`DC2`
19	00010011	0x13	0o023	`DC3`
20	00010100	0x14	0o024	`DC4`
21	00010101	0x15	0o025	`NAK`
22	00010110	0x16	0o026	`SYN`
23	00010111	0x17	0o027	`ETB`
24	00011000	0x18	0o030	`CAN`
25	00011001	0x19	0o031	`EM`
26	00011010	0x1A	0o032	`SUB`
27	00011011	0x1B	0o033	`ESC`
28	00011100	0x1C	0o034	`FS`
29	00011101	0x1D	0o035	`GS`
30	00011110	0x1E	0o036	`RS`
31	00011111	0x1F	0o037	`US`
32	00100000	0x20	0o040	`SP`
33	00100001	0x21	0o041	!
34	00100010	0x22	0o042	"
35	00100011	0x23	0o043	#
36	00100100	0x24	0o044	$
37	00100101	0x25	0o045	%
38	00100110	0x26	0o046	&
39	00100111	0x27	0o047	'
40	00101000	0x28	0o050	(
41	00101001	0x29	0o051	)
42	00101010	0x2A	0o052	*
43	00101011	0x2B	0o053	+
44	00101100	0x2C	0o054	,
45	00101101	0x2D	0o055	-
46	00101110	0x2E	0o056	.
47	00101111	0x2F	0o057	/
48	00110000	0x30	0o060	0
49	00110001	0x31	0o061	1
50	00110010	0x32	0o062	2
51	00110011	0x33	0o063	3
52	00110100	0x34	0o064	4
53	00110101	0x35	0o065	5
54	00110110	0x36	0o066	6
55	00110111	0x37	0o067	7
56	00111000	0x38	0o070	8
57	00111001	0x39	0o071	9
58	00111010	0x3A	0o072	:
59	00111011	0x3B	0o073	;
60	00111100	0x3C	0o074	<
61	00111101	0x3D	0o075	=
62	00111110	0x3E	0o076	>
63	00111111	0x3F	0o077	?

64–127

Decimal	Binary	Hex	Octal	ASCII
64	01000000	0x40	0o100	@
65	01000001	0x41	0o101	A
66	01000010	0x42	0o102	B
67	01000011	0x43	0o103	C
68	01000100	0x44	0o104	D
69	01000101	0x45	0o105	E
70	01000110	0x46	0o106	F
71	01000111	0x47	0o107	G
72	01001000	0x48	0o110	H
73	01001001	0x49	0o111	I
74	01001010	0x4A	0o112	J
75	01001011	0x4B	0o113	K
76	01001100	0x4C	0o114	L
77	01001101	0x4D	0o115	M
78	01001110	0x4E	0o116	N
79	01001111	0x4F	0o117	O
80	01010000	0x50	0o120	P
81	01010001	0x51	0o121	Q
82	01010010	0x52	0o122	R
83	01010011	0x53	0o123	S
84	01010100	0x54	0o124	T
85	01010101	0x55	0o125	U
86	01010110	0x56	0o126	V
87	01010111	0x57	0o127	W
88	01011000	0x58	0o130	X
89	01011001	0x59	0o131	Y
90	01011010	0x5A	0o132	Z
91	01011011	0x5B	0o133	[
92	01011100	0x5C	0o134	\
93	01011101	0x5D	0o135	]
94	01011110	0x5E	0o136	^
95	01011111	0x5F	0o137	_
96	01100000	0x60	0o140	`
97	01100001	0x61	0o141	a
98	01100010	0x62	0o142	b
99	01100011	0x63	0o143	c
100	01100100	0x64	0o144	d
101	01100101	0x65	0o145	e
102	01100110	0x66	0o146	f
103	01100111	0x67	0o147	g
104	01101000	0x68	0o150	h
105	01101001	0x69	0o151	i
106	01101010	0x6A	0o152	j
107	01101011	0x6B	0o153	k
108	01101100	0x6C	0o154	l
109	01101101	0x6D	0o155	m
110	01101110	0x6E	0o156	n
111	01101111	0x6F	0o157	o
112	01110000	0x70	0o160	p
113	01110001	0x71	0o161	q
114	01110010	0x72	0o162	r
115	01110011	0x73	0o163	s
116	01110100	0x74	0o164	t
117	01110101	0x75	0o165	u
118	01110110	0x76	0o166	v
119	01110111	0x77	0o167	w
120	01111000	0x78	0o170	x
121	01111001	0x79	0o171	y
122	01111010	0x7A	0o172	z
123	01111011	0x7B	0o173	{
124	01111100	0x7C	0o174	\|
125	01111101	0x7D	0o175	}
126	01111110	0x7E	0o176	~
127	01111111	0x7F	0o177	`DEL`

128–191

Decimal	Binary	Hex	Octal	ASCII
128	10000000	0x80	0o200	—
129	10000001	0x81	0o201	—
130	10000010	0x82	0o202	—
131	10000011	0x83	0o203	—
132	10000100	0x84	0o204	—
133	10000101	0x85	0o205	—
134	10000110	0x86	0o206	—
135	10000111	0x87	0o207	—
136	10001000	0x88	0o210	—
137	10001001	0x89	0o211	—
138	10001010	0x8A	0o212	—
139	10001011	0x8B	0o213	—
140	10001100	0x8C	0o214	—
141	10001101	0x8D	0o215	—
142	10001110	0x8E	0o216	—
143	10001111	0x8F	0o217	—
144	10010000	0x90	0o220	—
145	10010001	0x91	0o221	—
146	10010010	0x92	0o222	—
147	10010011	0x93	0o223	—
148	10010100	0x94	0o224	—
149	10010101	0x95	0o225	—
150	10010110	0x96	0o226	—
151	10010111	0x97	0o227	—
152	10011000	0x98	0o230	—
153	10011001	0x99	0o231	—
154	10011010	0x9A	0o232	—
155	10011011	0x9B	0o233	—
156	10011100	0x9C	0o234	—
157	10011101	0x9D	0o235	—
158	10011110	0x9E	0o236	—
159	10011111	0x9F	0o237	—
160	10100000	0xA0	0o240	—
161	10100001	0xA1	0o241	—
162	10100010	0xA2	0o242	—
163	10100011	0xA3	0o243	—
164	10100100	0xA4	0o244	—
165	10100101	0xA5	0o245	—
166	10100110	0xA6	0o246	—
167	10100111	0xA7	0o247	—
168	10101000	0xA8	0o250	—
169	10101001	0xA9	0o251	—
170	10101010	0xAA	0o252	—
171	10101011	0xAB	0o253	—
172	10101100	0xAC	0o254	—
173	10101101	0xAD	0o255	—
174	10101110	0xAE	0o256	—
175	10101111	0xAF	0o257	—
176	10110000	0xB0	0o260	—
177	10110001	0xB1	0o261	—
178	10110010	0xB2	0o262	—
179	10110011	0xB3	0o263	—
180	10110100	0xB4	0o264	—
181	10110101	0xB5	0o265	—
182	10110110	0xB6	0o266	—
183	10110111	0xB7	0o267	—
184	10111000	0xB8	0o270	—
185	10111001	0xB9	0o271	—
186	10111010	0xBA	0o272	—
187	10111011	0xBB	0o273	—
188	10111100	0xBC	0o274	—
189	10111101	0xBD	0o275	—
190	10111110	0xBE	0o276	—
191	10111111	0xBF	0o277	—

192–255

Decimal	Binary	Hex	Octal	ASCII
192	11000000	0xC0	0o300	—
193	11000001	0xC1	0o301	—
194	11000010	0xC2	0o302	—
195	11000011	0xC3	0o303	—
196	11000100	0xC4	0o304	—
197	11000101	0xC5	0o305	—
198	11000110	0xC6	0o306	—
199	11000111	0xC7	0o307	—
200	11001000	0xC8	0o310	—
201	11001001	0xC9	0o311	—
202	11001010	0xCA	0o312	—
203	11001011	0xCB	0o313	—
204	11001100	0xCC	0o314	—
205	11001101	0xCD	0o315	—
206	11001110	0xCE	0o316	—
207	11001111	0xCF	0o317	—
208	11010000	0xD0	0o320	—
209	11010001	0xD1	0o321	—
210	11010010	0xD2	0o322	—
211	11010011	0xD3	0o323	—
212	11010100	0xD4	0o324	—
213	11010101	0xD5	0o325	—
214	11010110	0xD6	0o326	—
215	11010111	0xD7	0o327	—
216	11011000	0xD8	0o330	—
217	11011001	0xD9	0o331	—
218	11011010	0xDA	0o332	—
219	11011011	0xDB	0o333	—
220	11011100	0xDC	0o334	—
221	11011101	0xDD	0o335	—
222	11011110	0xDE	0o336	—
223	11011111	0xDF	0o337	—
224	11100000	0xE0	0o340	—
225	11100001	0xE1	0o341	—
226	11100010	0xE2	0o342	—
227	11100011	0xE3	0o343	—
228	11100100	0xE4	0o344	—
229	11100101	0xE5	0o345	—
230	11100110	0xE6	0o346	—
231	11100111	0xE7	0o347	—
232	11101000	0xE8	0o350	—
233	11101001	0xE9	0o351	—
234	11101010	0xEA	0o352	—
235	11101011	0xEB	0o353	—
236	11101100	0xEC	0o354	—
237	11101101	0xED	0o355	—
238	11101110	0xEE	0o356	—
239	11101111	0xEF	0o357	—
240	11110000	0xF0	0o360	—
241	11110001	0xF1	0o361	—
242	11110010	0xF2	0o362	—
243	11110011	0xF3	0o363	—
244	11110100	0xF4	0o364	—
245	11110101	0xF5	0o365	—
246	11110110	0xF6	0o366	—
247	11110111	0xF7	0o367	—
248	11111000	0xF8	0o370	—
249	11111001	0xF9	0o371	—
250	11111010	0xFA	0o372	—
251	11111011	0xFB	0o373	—
252	11111100	0xFC	0o374	—
253	11111101	0xFD	0o375	—
254	11111110	0xFE	0o376	—
255	11111111	0xFF	0o377	—

Powers of two

The numbers that appear constantly in memory sizes, address ranges and limits.

Power	Decimal	Hex	Significance
2⁰	1	0x1	One bit
2¹	2	0x2
2²	4	0x4
2³	8	0x8	One byte’s worth of values per nibble
2⁴	16	0x10
2⁵	32	0x20	Case bit in ASCII
2⁶	64	0x40
2⁷	128	0x80	ASCII range
2⁸	256	0x100	One byte
2⁹	512	0x200
2¹⁰	1,024	0x400	1 KiB
2¹¹	2,048	0x800
2¹²	4,096	0x1000
2¹³	8,192	0x2000
2¹⁴	16,384	0x4000
2¹⁵	32,768	0x8000
2¹⁶	65,536	0x10000	16-bit range, 64 KiB
2²⁰	1,048,576	0x100000	1 MiB
2²⁴	16,777,216	0x1000000	RGB colour space
2³⁰	1,073,741,824	0x40000000	1 GiB
2³¹	2,147,483,648	0x80000000	Signed 32-bit limit
2³²	4,294,967,296	0x100000000	IPv4 address space
2⁴⁰	1,099,511,627,776	0x10000000000	1 TiB
2⁵³	9,007,199,254,740,992	0x20000000000000	JavaScript exact integer limit
2⁶⁴	18,446,744,073,709,551,616	0x10000000000000000	64-bit range

Boundary values that cause bugs

Value	Why it matters
127	Largest signed 8-bit integer; largest ASCII code
128	Most negative signed 8-bit value (−128); first “extended” byte
255	Largest unsigned byte; `0xFF`; full colour channel
32,767	Largest signed 16-bit integer
65,535	Largest unsigned 16-bit; highest TCP/UDP port
2,147,483,647	Largest signed 32-bit integer; the 2038 timestamp limit
4,294,967,295	Largest unsigned 32-bit; total IPv4 addresses
9,007,199,254,740,991	JavaScript `MAX_SAFE_INTEGER`, 2⁵³−1

Off-by-one errors around these values are among the most common classes of bug in systems programming. The Y2K38 problem is exactly the 2,147,483,647 row: 32-bit Unix timestamps overflow on 19 January 2038, as explained in the timestamp converter.

Frequently Asked Questions

How do I convert binary to decimal?

Multiply each bit by its positional value (1, 2, 4, 8, 16…) and add them up. 1101 is 8 + 4 + 0 + 1 = 13. The chart lets you look it up directly.

How many hex digits make a byte?

Two. Each hex digit represents exactly four bits, so FF is 11111111, which is 255.

Why is 255 significant?

It is the largest value one unsigned byte can hold, which is why colour channels, IP octets and many size limits stop there.

What is 0xFF in decimal?

255. The 0x prefix marks hexadecimal, and FF is 15×16 + 15.

Why does octal use three bits per digit?

Because octal is base 8 and 8 = 2³. Each octal digit maps to exactly three binary digits, which is why Unix file permissions are written in octal.

What is the largest 32-bit signed integer?

2,147,483,647. One bit is the sign, leaving 31 bits of magnitude. This value is the cause of the Year 2038 problem in 32-bit Unix timestamps.

Sources & further reading

Positional notation — the general principle behind every base in this chart
The Year 2038 problem — what happens when a signed 32-bit counter overflows
MDN: MAX_SAFE_INTEGER — the exact-integer limit in JavaScript