What is Number Base Converter?
Number Base Converter converts whole numbers between binary, octal, decimal, hexadecimal, and custom bases from 2 to 36.
How to use it
Enter an integer, choose the input base or Auto Detect for 0b, 0o, and 0x prefixes, choose an output base, then press Convert. The main result and the common base table can be copied separately.
How it works
The converter validates each digit for the selected base, parses the integer into a BigInt without using JavaScript Number for the entered value, and formats that exact BigInt into the requested base.
Is data saved?
Your input is processed locally in your browser and is not uploaded to a server.
What is a number base?
A number base defines which digits can be used and how much each digit position is worth. Base 10 is the everyday decimal system, while computers often use base 2 and base 16 because they map cleanly to bits and bytes.
Binary, octal, decimal, and hexadecimal
Binary uses only 0 and 1. Octal uses 0 through 7. Decimal uses 0 through 9. Hexadecimal uses 0-9 and A-F, so it is common in programming, memory addresses, color codes, binary data, and debugging.
Custom bases from 2 to 36
For bases above 10, letters represent digit values: A is 10, B is 11, and Z is 35. Input accepts uppercase or lowercase letters, and results can be shown in uppercase or lowercase.
Conversion examples
Use the examples to check familiar conversions before converting your own values.
- Decimal 255 becomes binary 11111111, octal 377, and hexadecimal FF.
- Binary 101010 becomes decimal 42.
- Hexadecimal 7B becomes decimal 123.
- Decimal -64 becomes binary -1000000.
Common use cases
Base conversion is useful when reading low-level data or moving between human-friendly and machine-friendly representations.
- Convert decimal values to binary for bit masks and flags.
- Convert hexadecimal values to decimal while debugging API payloads or logs.
- Convert color or memory-related hex values into a format that is easier to inspect.
- Check custom base values for coding challenges, tests, and data encoding exercises.
Precision with very large integers
The tool uses BigInt and a manual parser, so integers larger than 9007199254740991 are not rounded by JavaScript Number. Fractional values such as 10.5 are intentionally rejected in this version.