A number base converter converts a number from one positional numeral system to another. The most common bases in computing are binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16). Each base uses a different set of digits: binary uses 0–1, octal uses 0–7, decimal uses 0–9, and hexadecimal uses 0–9 and A–F.

1. Enter the number to convert.
2. Select the base of the input number.
3. Click Convert to see the equivalent in binary, octal, decimal and hexadecimal.

Decimal 255 = Binary 11111111 = Octal 377 = Hex FF
Binary 1010 = Decimal 10 = Hex A = Octal 12

Binary is the native language of computers — all data is ultimately stored as 0s and 1s. Hexadecimal is a compact representation of binary (each hex digit represents 4 binary digits). Octal was used in older systems and is still seen in Unix file permissions. Decimal is the everyday human number system.

• Entering letters in a binary or octal number — binary only uses 0 and 1; octal uses 0–7.
• Confusing the base of the input — always select the correct source base before converting.

What does 0xFF mean?

0xFF is hexadecimal notation for the decimal number 255. In binary it is 11111111 — all 8 bits set to 1, which is the maximum value of an unsigned byte.

Why do programmers use hexadecimal?

Each hexadecimal digit represents exactly 4 binary digits (bits). This makes hex a compact and readable way to represent binary data — a byte (8 bits) is always exactly 2 hex digits.

What is the largest number this converter supports?

The converter uses JavaScript's integer parsing, which supports integers up to 2^53 − 1 (9,007,199,254,740,991) accurately. Very large numbers may lose precision.