Convert a whole number between binary, octal, decimal, hexadecimal or any base from 2 to 36. Prefixes such as 0x, 0b and 0o are recognised, and very long numbers stay exact.
Every base writes numbers with place values that are powers of the base. In binary the places are 1, 2, 4, 8, 16 and so on, so 1101 is 8 + 4 + 1 = 13. Hexadecimal uses the digits 0 to 9 and A to F for 10 to 15, so FF is 15 × 16 + 15 = 255.
The converter uses whole-number arithmetic with no rounding, so values with hundreds of digits are converted exactly.
The box on the Convert page answers the same questions as you type, for example “120000 in words”, “1994 in roman”, “255 in binary” or “0.375 as a fraction”.
| Decimal | Binary | Octal | Hexadecimal |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 1 | 1 | 1 | 1 |
| 2 | 10 | 2 | 2 |
| 7 | 111 | 7 | 7 |
| 8 | 1000 | 10 | 8 |
| 10 | 1010 | 12 | A |
| 15 | 1111 | 17 | F |
| 16 | 1 0000 | 20 | 10 |
| 32 | 10 0000 | 40 | 20 |
| 64 | 100 0000 | 100 | 40 |
| 100 | 110 0100 | 144 | 64 |
| 127 | 111 1111 | 177 | 7F |
| 128 | 1000 0000 | 200 | 80 |
| 255 | 1111 1111 | 377 | FF |
| 256 | 1 0000 0000 | 400 | 100 |
| 1,000 | 11 1110 1000 | 1750 | 3E8 |
| 1,024 | 100 0000 0000 | 2000 | 400 |
| 4,096 | 1 0000 0000 0000 | 10000 | 1000 |
| 65,535 | 1111 1111 1111 1111 | 177777 | FFFF |
Divide by 2 repeatedly and write the remainders from last to first. 13 ÷ 2 = 6 remainder 1, 6 ÷ 2 = 3 remainder 0, 3 ÷ 2 = 1 remainder 1 and 1 ÷ 2 = 0 remainder 1, so 13 is 1101.
They are prefixes used in programming: 0x marks hexadecimal (0xFF = 255), 0b binary (0b1010 = 10) and 0o octal (0o17 = 15). The converter recognises them automatically.
Numbers of up to 256 digits are converted exactly, because the converter uses whole-number arithmetic with no rounding.