Number Base Converter

Convert between hexadecimal, decimal, binary and octal. Type into any box and the other three update as you go.

All base conversions

decimal to hex decimal to binary decimal to octal hex to decimal hex to binary hex to octal binary to decimal binary to hex binary to octal octal to decimal octal to hex octal to binary

Hex, decimal, binary and octal reference table

The values programmers look up most: every single hex digit, the byte boundaries and the power-of-two edges.

Number base reference table
Decimal	Hexadecimal	Binary	Octal
0	0	0	0
1	1	1	1
2	2	10	2
3	3	11	3
4	4	100	4
5	5	101	5
6	6	110	6
7	7	111	7
8	8	1000	10
9	9	1001	11
10	A	1010	12
11	B	1011	13
12	C	1100	14
13	D	1101	15
14	E	1110	16
15	F	1111	17
16	10	10000	20
32	20	100000	40
64	40	1000000	100
100	64	1100100	144
127	7F	1111111	177
128	80	10000000	200
255	FF	11111111	377
256	100	100000000	400
512	200	1000000000	1000
1000	3E8	1111101000	1750
1023	3FF	1111111111	1777
1024	400	10000000000	2000
4095	FFF	111111111111	7777
4096	1000	1000000000000	10000
65535	FFFF	1111111111111111	177777
65536	10000	10000000000000000	200000

Decimal (base 10)

Decimal is base 10, the everyday number system, using the digits 0 to 9. Each place is worth ten times the one to its right.

Hexadecimal (base 16)

Hexadecimal is base 16, using 0 to 9 then A to F for the values ten to fifteen. One hex digit encodes exactly four bits, so a byte is always two hex digits — which is why colours, memory addresses and hashes are written in hex.

Binary (base 2)

Binary is base 2, using only 0 and 1. It is how every digital computer physically stores and manipulates data, with each digit representing one bit.

Octal (base 8)

Octal is base 8, using the digits 0 to 7. One octal digit encodes exactly three bits, which is why Unix file permissions are written as octal numbers such as 755.

Frequently asked questions

How do you convert hex to decimal by hand?

Multiply each hex digit by 16 raised to its position, counting from zero on the right, and add the results. For 1F: (1 × 16) + (15 × 1) = 31. The letter F stands for fifteen.

Why do programmers use hexadecimal?

One hex digit maps to exactly four bits, so a byte is always exactly two hex digits and nothing is ever ambiguous. Writing the same byte in decimal takes one, two or three digits, which makes memory dumps and colour codes far harder to read.

What do the prefixes 0x, 0b and 0o mean?

They tell a compiler which base a literal is written in: 0x for hexadecimal, 0b for binary and 0o for octal. 0x10, 0b10000 and 16 are all the same number. This converter accepts the prefixes and ignores them.

How large a number can this convert?

There is no practical limit. Conversions use arbitrary-precision integers, so 64-bit and larger values convert exactly instead of losing precision the way ordinary floating point arithmetic would above about 9 quadrillion.