Convert integers between binary, octal, decimal, and hexadecimal with exact BigInt arithmetic — no rounding, fully local.
The number base converter translates integers between the four bases programmers actually use: binary (2), octal (8), decimal (10), and hexadecimal (16). Type a value in one base, pick the target base, and the tool returns the exact equivalent — 255 in decimal becomes ff in hexadecimal, 755 in octal, and 11111111 in binary. The arithmetic runs on BigInt, so conversion is exact for any magnitude: a 64-bit value like FFFFFFFFFFFFFFFF converts to 18446744073709551615 without the rounding or precision loss that plagues floating-point converters. Input is forgiving in the right ways: a leading minus sign is honored, and a literal prefix that matches the source base — 0x for hexadecimal, 0b for binary, 0o for octal — is stripped automatically, so values copied out of a debugger or a C-style constant work as pasted. Digits are validated strictly against the source base: 2 in binary or 8 in octal is rejected with a message that says which digits are allowed, rather than silently producing a wrong answer. Conversion of integers is exact by definition — this tool never approximates, and nothing you enter is uploaded, logged, or stored. Use it when you are decoding a bitmask, reading a memory dump, checking a hash prefix, translating an IPv4 octet, or any time a value in one base needs to become another.
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Converted
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Exact BigInt arithmetic — a 64-bit value converts without rounding. Integers only; hex output is lowercase.
A config file enables features through a decimal bitmask, 490. To see which bits are on, convert 490 from decimal to binary: the result is 111101010 — bits 1, 3, 5, 6, 7, and 8 are set, counting from bit 1 at the right.
| Input | Value |
|---|---|
| value | 490 |
| fromBase | 10 |
| toBase | 2 |
| Result | 111101010 |
value = Σ digitᵢ × baseⁱ (then re-render in the target base)
| Symbol | Meaning |
|---|---|
digitᵢ | the digit at position i, from the right, in the source base |
base | the source base: 2, 8, 10, or 16 |
re-render | dividing the value by the target base and collecting remainders, producing the target-base digits |
The tool converts with BigInt, so every intermediate step is exact regardless of magnitude.
Last reviewed August 11, 2026 · Version 1.0.0 · Toolivaro does not guarantee external content.
A 64-bit integer like 18446744073709551615 cannot be represented exactly in a 53-bit floating-point number — it would round to 18446744073709552000, a wrong answer. BigInt is exact at any magnitude, so the converter never silently rounds.
Yes. A leading 0x, 0b, or 0o is stripped automatically when it matches the selected source base — 0x1A in hexadecimal is read as 1A. A prefix that contradicts the source base is treated as an invalid digit and rejected.
Hexadecimal is case-insensitive — ff and FF are the same value. The converter emits lowercase, the convention used by most tooling, and accepts either case as input.
No. Fractional bases are a different problem (repeating digits are the norm — 0.1 in binary is infinite), so the converter is integer-only and rejects anything that is not a whole number with a clear error.
Part of Format and conversion tools
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