About Number Base Converter – Binary, Hex, Decimal
This free number base converter turns integers between binary, octal, decimal, hexadecimal, and any radix from base 2 to base 36. Switch to Common mode to see a value in all four standard bases at once and live, or use Arbitrary mode to convert between any two bases — handy for color codes, bitmasks, byte values, and base-36 short IDs.
Every conversion is backed by JavaScript's BigInt, so even very large numbers (hundreds of digits) are exact, with no floating-point rounding or overflow. Negative values are supported too.
It runs entirely in your browser and works offline. Whatever you type — keys, IDs, or sensitive constants — never leaves your device.
Features
- See binary, octal, decimal, and hex simultaneously and live
- Convert between any two bases from 2 to 36
- Exact for arbitrarily large integers via BigInt — no rounding
- Handles negative numbers; clear errors on invalid digits; fully offline
How to use
- Pick a mode: "Common bases" to see all four at once, or "Arbitrary" for any base pair.
- In Common mode, choose the input base and type your number — BIN/OCT/DEC/HEX update instantly.
- In Arbitrary mode, set the from-base and to-base steppers (2–36) and read the result.
- Copy any field with its copy button.
Frequently asked questions
How do I convert binary to decimal?
Select Common mode, set the input base to Binary (2), and type your binary digits. The decimal value appears instantly in the DEC field, alongside octal and hex. Or use Arbitrary mode with from-base 2 and to-base 10.
What is the largest number it can convert?
There is no practical limit. The converter uses BigInt arithmetic, so integers with hundreds of digits are converted exactly — no floating-point rounding and no overflow.
What does base 36 mean?
Base 36 uses the digits 0–9 followed by the letters a–z, giving 36 symbols per place. It is the most compact base that stays alphanumeric, which is why it is popular for short URLs and IDs.
Can it handle negative numbers?
Yes. Prefix the value with a minus sign ("-") and the negative is preserved in every target base.
Does my data get sent to a server?
No. All parsing and formatting happens locally in your browser. Nothing you enter is uploaded, so the tool works fully offline.
Related tools
Everything runs locally in your browser — your input is never uploaded.