Number Base Converter

Number Base Converter instantly converts any whole number between binary, octal, decimal and hexadecimal. Type a value, pick its base, and see all four representations at once. All processing happens locally in your browser, and nothing is sent to a server.

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About Number Base Conversion

Number base (or radix) conversion expresses the same value in different numeral systems. Binary (base 2) uses 0-1, octal (base 8) uses 0-7, decimal (base 10) uses 0-9, and hexadecimal (base 16) uses 0-9 and a-f.

This converter uses arbitrary-precision integers, so very large numbers convert accurately without rounding errors.

Base conversion shows up everywhere in programming: memory addresses and colour codes in hexadecimal, file permissions in octal, and bitmasks or flags in binary. Hexadecimal stays popular because two hex digits map neatly onto one byte, which makes raw data compact and easy to scan.

Set a register width and negative numbers stop being a minus sign in front of a magnitude and become the bit pattern the hardware actually holds, which is what a debugger shows you and what a protocol on the wire carries. The bit row underneath spells that pattern out in full, padded to the width, so a value like -1 reads as a run of ones rather than as a number. Everything is computed with arbitrary precision integers, so a 64 bit value stays exact instead of rounding above 2^53.

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Frequently Asked Questions

Is this number base converter free and private?
Yes. It is completely free and runs entirely in your browser, so the numbers you convert are never uploaded or stored on any server.
How large a number can it convert?
It uses arbitrary-precision (BigInt) arithmetic, so it converts very large integers between binary, octal, decimal and hexadecimal without rounding or overflow errors.
Can it convert negative numbers or hex with a 0x prefix?
Yes. Negative values are supported, and common prefixes like 0x, 0b and 0o are accepted; spaces and underscores in the input are ignored.
Which bases can I convert to?
Binary, octal, decimal and hexadecimal are always shown, and the extra row does any base from 2 to 36 using digits and then letters. Base 36 is the densest a number can be written with the plain alphabet, which is why short identifiers often use it.
Why does the copy button strip the grouping?
Because grouping is there to be read, not pasted. The spaces and commas that make a long binary value legible would be rejected by anything you paste it into, so copying gives you the bare digits.