Convert a number between binary, octal, decimal, hexadecimal and any base from 2 to 36 — all at once. Type in any base and the rest update instantly, with arbitrary-precision math for huge numbers.
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A whole number is one quantity written many ways. Decimal (base 10) is what we count in day to day; binary (base 2) is how computers store it; hexadecimal (base 16) is the compact shorthand programmers use for bytes, colors and memory addresses; and octal (base 8) still shows up in file permissions. They all describe the same value — only the number of distinct digits changes. This tool shows every common base at once and keeps them in sync: type in any base and the rest follow, exactly, even for enormous numbers.
| Base | Digits used | Example (decimal 45) |
|---|---|---|
| Binary (2) | 0 1 | 101101 |
| Octal (8) | 0–7 | 55 |
| Decimal (10) | 0–9 | 45 |
| Hexadecimal (16) | 0–9 A–F | 2D |
| Base 36 | 0–9 A–Z | 19 |
Each digit position is worth the base raised to a power. In binary, 101101 means 1·32 + 0·16 + 1·8 + 1·4 + 0·2 + 1·1 = 45. In hex, 2D means 2·16 + 13 = 45. The converter does this for you in both directions — parse a number out of one base into an exact value, then render that value into every other base. Digits beyond 9 use letters, so A=10, B=11, up to Z=35 in base 36.
Ordinary JavaScript numbers lose precision above 2⁵³, which quietly corrupts long hex hashes or big decimals. This tool uses arbitrary-precision integer math (BigInt), so a 256-bit value converts between bases with no rounding at all. It also accepts a leading minus sign for negative integers, and ignores spaces and underscores so you can paste grouped values like 1010_1101 or FF FF.
Pick the base you are typing in with the chips on the left — or choose Custom to enter any radix from 2 to 36. Turn on nibble grouping to read long binary in 4-bit blocks, the way bytes are usually written. Every result has a Copy button for one-click paste into code. The readout under the input shows the decimal value plus how many bits and bytes the number needs.
Yes. Every conversion runs as plain JavaScript inside your browser — no server call, no upload, nothing logged or stored. Whatever you enter never leaves your device. Refresh the page and it is gone.