Base & binary converter

Convert number bases and convert text to and from binary or hex, all inside this browser.

Number base conversion

Use it to change the base of a number or to check the actual bytes of text when working with programming, networking or character encodings.

Numbers: enter a number and choose its base to see the binary, octal, decimal and hexadecimal values plus the extra base you pick.
Text: choose the direction and byte notation, then type; the result appears immediately.
When you press a copy button, the confirmation appears only after copying succeeds.

Example: 255 FF decimal to hexadecimal

Number input is limited to 1,000 characters and is calculated with BigInt, so even very large integers are exact.
Only integers are supported. Decimal points and exponent notation are reported as errors.
Letters in numbers are case-insensitive and results are shown in uppercase. A prefix matching the input base (0x, 0b, 0o) is allowed.
Text is always handled as UTF-8 bytes. Korean letters take 3 bytes each and emoji usually take 4.
Bytes can be separated by spaces, commas or line breaks, or written together as 8 binary digits or 2 hex digits each.
Bytes that are not valid UTF-8 and unpaired character fragments are reported as errors, never silently replaced.

Is my input sent to a server?

No. Every conversion runs inside this browser, and your input and results are neither saved nor uploaded. They disappear when you reload.

How are negative numbers shown?

They are shown as a sign and an absolute value, not as two's complement. For example, -255 is -FF in hexadecimal.

Why does Korean take 3 bytes?

UTF-8 uses 1 to 4 bytes per character and a Korean syllable takes 3. For example, the syllable “ga” is EA B0 80.