Free Online Number Base Converter

About the Number Base Converter

A number base, or radix, is the count of distinct digits a numeral system uses. Binary (base 2) is how digital circuits store values. Octal (base 8) and hexadecimal (base 16) are compact ways to write binary because each digit maps to exactly three or four bits. Decimal (base 10) is the everyday system, and bases up to 36 appear in identifiers, encodings, and puzzles. This tool converts an integer between any two bases from 2 to 36.

How positional notation works

Each digit is multiplied by the base raised to its position, counting from zero on the right. For example, 1011 in binary is 1×8 + 0×4 + 1×2 + 1×1 = 11 in decimal. Hexadecimal uses letters for values above nine: A is 10, B is 11, up to F for 15. Base 36 uses all ten digits plus A through Z.

JavaScript's native Number type loses precision beyond 2⁵³−1. This converter uses BigInt instead, so large integers such as 128-bit identifiers, cryptographic constants, and database keys are converted exactly with no rounding. The parser validates every digit against the input base and reports the first invalid character. Negative values are supported with a leading minus sign.

Common uses include reading memory addresses and color values in hexadecimal, checking permission masks in octal, building packet dumps in binary, and generating short identifiers in higher bases. Remember that a conversion only changes the representation, not the value. If you paste a value with a prefix such as 0x, choose the matching base first; a mismatched prefix will be reported as an invalid digit.

How to use this tool

1. Enter an integer in the number field.
2. Set the input base from 2 to 36.
3. Choose a custom output base, or read the standard binary, octal, decimal, and hex results.
4. Copy an individual value or all results.

Frequently asked questions