Binary to Decimal Converter

Convert numbers between binary (base 2) and decimal (base 10), with hexadecimal and octal shown too. Enter the number and choose the base it is written in.

How to use the Binary to Decimal Converter

Type the number.
Choose the base it is in — binary, decimal, hex or octal.
Read the number in every other base.

How it works

Binary to decimal: each binary digit (bit) is worth a power of two, doubling from right to left: 1, 2, 4, 8, 16… Add the values of the 1 bits. 101010 = 32 + 8 + 2 = 42.

Decimal to binary: divide by 2 repeatedly and write down the remainders; reading them from bottom to top gives the binary number. 42 → 21 r0 → 10 r1 → 5 r0 → 2 r1 → 1 r0 → 0 r1 → 101010.

Decimal to binary chart

Decimal	Binary	Decimal	Binary
0	0000	8	1000
1	0001	9	1001
2	0010	10	1010
3	0011	11	1011
4	0100	12	1100
5	0101	13	1101
6	0110	14	1110
7	0111	15	1111

Frequently asked questions

What is 1010 in decimal?

10 (8 + 2).

What is 255 in binary?

11111111 — eight 1 bits, the largest value in one byte.

Why do computers use binary?

Digital circuits have two stable states, on and off, which map naturally to 1 and 0.

How many values can 8 bits hold?

256 values, from 0 to 255.