Number base converter
Convert integers between decimal, binary, octal and hexadecimal.
How to use
- Paste integers, one per line — decimal, or prefixed (0x…, 0b…, 0o…).
- Choose the target base; → Decimal converts prefixed values back.
- Copy the converted column from the result pane.
Frequently asked questions
How large can the numbers be?
Effectively unlimited. Conversion uses BigInt arithmetic, so 64-bit and larger values convert exactly — no rounding at 2⁵³ like ordinary JavaScript numbers.
How do I convert from hex or binary to decimal?
Prefix the value (0xff, 0b1010, 0o17) and choose → Decimal. The prefix tells the parser which base to read.
Are fractions supported?
No, only integers. Fractional base conversion is rarely needed and is ambiguous to round; lines with decimals show as "?".
About this tool
Programmers juggle number bases constantly: permissions in octal, colors and memory addresses in hex, bit masks in binary. This converter moves integers between all four bases. Input is flexible — plain decimal, or prefixed values like 0xff, 0b1010 and 0o17 — and each line converts independently, so a column of values converts in one click. Arithmetic uses BigInt, meaning very large values (beyond JavaScript's 2⁵³ safe-integer limit) convert exactly with no silent precision loss, which matters for 64-bit addresses and IDs. Negative values keep their sign across bases.