Number Systems
42 integer-base + numeral-system converters: decimal / binary / octal / hex / Roman / English words / scientific notation.
34 tools available
Number Systems tools convert integers between positional bases and numeral systems: decimal, binary, octal, hexadecimal, arbitrary bases, Roman numerals, English number words, and scientific notation. They make the abstract idea of “base” concrete by showing the same value in every representation side by side.
A positional system is just a set of digits and a base. Decimal (base 10) uses ten digits; binary (base 2) uses two and is how computers store everything; hexadecimal (base 16) is a compact human shorthand for binary, where one hex digit equals exactly four bits. Converting between them is mechanical but error-prone by hand, which is where these tools earn their place — for reading memory dumps, setting permission bits, decoding colour codes, or simply understanding how the same quantity wears different clothes. Everything is computed live in your browser.
The same value across bases
Decimal 42 shown in the common positional systems.
| System | Base | Digits used | 42 in this base |
|---|---|---|---|
| Binary | 2 | 0–1 | 101010 |
| Octal | 8 | 0–7 | 52 |
| Decimal | 10 | 0–9 | 42 |
| Hexadecimal | 16 | 0–9 A–F | 2A |
| Roman | — | I V X L C… | XLII |
One hexadecimal digit maps to exactly four binary bits, which is why hex is the go-to shorthand for binary.