Number Base Converter
Convert between binary, octal, decimal, hexadecimal and any base from 2 to 36.
Convert Between Binary, Octal, Decimal and Hexadecimal
Programmers move between number bases constantly. Binary shows what the hardware actually stores, hexadecimal compresses four bits into one readable digit, octal survives in Unix file permissions, and decimal is what humans think in. Colour codes, memory addresses, bitmasks and file modes all depend on reading the right base.
This converter takes a value in any base from 2 to 36 and shows it in all the common bases at once, plus any custom base you choose. Invalid digits are rejected with an explanation rather than silently producing a wrong answer.
Key features
- Any base from 2 to 36 — the standard bases as tabs, plus a custom base field.
- All outputs at once — binary, octal, decimal, hex, base 32 and base 36 side by side.
- Digit validation — entering "2" in binary or "G" in hex is caught and explained.
- Precision guard — values beyond 2^53 are refused rather than converted inaccurately.
- Negative numbers — handled with a leading minus sign.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Number Base Converter
- Enter your value
Type the number exactly as written in its own base — no prefix like 0x or 0b is needed. - Select the input base
Tell the converter what base your value is already in. This is the step people most often get wrong. - Read every output
All common bases appear at once, each with its own copy button. - Use a custom base if needed
Any base from 2 to 36 — base 36 uses digits 0-9 then A-Z.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Converters |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Why does hexadecimal use letters?
Base 16 needs sixteen distinct digits, but we only have ten numerals, so A through F stand for 10 to 15. Hex is popular because each digit maps to exactly four binary bits, making conversion to and from binary trivial.
How do I convert binary to decimal by hand?
Multiply each digit by two raised to its position from the right, starting at zero, and add them up. 1011 = 8 + 0 + 2 + 1 = 11.
Why is there a limit at 2^53?
JavaScript numbers are IEEE 754 doubles, which represent integers exactly only up to 9,007,199,254,740,991. Beyond that, conversions would silently round. The tool refuses rather than showing a wrong answer.
What is octal still used for?
Unix file permissions, most visibly. chmod 755 is octal: each digit encodes three permission bits for owner, group and others. Octal survives there because three bits map neatly onto one digit.