Toolkeel

Number base converter

Convert between binary, octal, decimal and hexadecimal (or any base up to 36). Type in any box and the others update instantly.

  • Free
  • Private
  • No sign-up

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  1. Your text and dataRead from your device
  2. Worked on in this tabBy code running in your browser
  3. Ready to copyNothing is stored

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How to use it

  1. Type a number in any of the boxes.

  2. The other bases update as you type.

  3. Set a custom base (2–36) if you need another one.

About this tool

Computers store numbers in binary; programmers often write them in hexadecimal (each hex digit is exactly four bits) or octal (Unix file permissions). Numbers are handled with JavaScript BigInt, so there is no 253 precision limit. Prefixes such as 0x, 0b and 0o and separators like spaces and underscores are accepted.

Good to know

  • Whole numbers only (no fractions).
  • Negative numbers are shown with a minus sign, not two’s complement.

Frequently asked questions

How do I convert hex to decimal?

Type the hex value (for example FF or 0xFF) in the hexadecimal box. The decimal value (255) appears instantly.

Is there a size limit?

No practical limit. Very large numbers are converted exactly.

What is base 36?

A system using digits 0–9 and letters a–z, often used for short IDs.

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Last updated 2026-10-20 by the Toolkeel team. How we build and check our tools.