Free Number Base Converter — Binary, Octal, Decimal & Hex

A base converter transforms numbers between different numeral systems — binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16) — simultaneously. Enter a number in any supported base and instantly see its representation in all four systems, along with the bit count and input validation.

Base conversion is essential in computer science, networking, and digital electronics. Whether you're reading memory addresses in hex, debugging binary flags, or converting between formats for a programming assignment, this tool handles the arithmetic instantly and shows all four representations side by side.

• Binary (base 2) - Convert to and from the fundamental language of computers and digital logic
• Octal (base 8) - Work with Unix file permissions and legacy computing formats that use octal notation
• Decimal (base 10) - Translate human-readable numbers into machine-friendly formats and back
• Hexadecimal (base 16) - Read and write memory addresses, color codes, MAC addresses, and byte values
• All bases at once - See binary, octal, decimal, and hex representations simultaneously for any input
• Bit count - Know exactly how many bits are needed to represent your number in binary

• Different digit sets - Binary uses only 0 and 1, octal uses 0–7, decimal uses 0–9, and hex uses 0–9 plus A–F, making it easy to mix up valid digits
• Manual division method is slow - Converting by hand requires repeated division and remainder tracking, which is tedious and error-prone for large numbers
• Hex letter digits cause confusion - Remembering that A=10, B=11, C=12, D=13, E=14, F=15 and applying this consistently adds cognitive load
• Input validation matters - Entering a digit that doesn't belong in the selected base (like 8 in octal or G in hex) produces meaningless results, so validation is critical

Enter a number and select the base you're typing in (binary, octal, decimal, or hexadecimal). The converter validates your input, then displays the equivalent value in all four bases simultaneously, along with the bit count (the number of binary digits needed). Common prefixes like 0b, 0o, and 0x are shown for clarity.

The tool accepts standard notation for each base and handles the conversion using standard positional arithmetic — expanding each digit by its place value in the source base, then converting to each target base.

Example

Entering 214 in decimal produces: 0b11010110 (binary) | 0o326 (octal) | 214 (decimal) | 0xD6 (hexadecimal). The bit count is 8, meaning 214 fits in a single byte.

• Web development - Convert decimal RGB values to hexadecimal color codes (e.g., 255 → FF)
• Networking - Translate IP addresses and subnet masks between decimal and binary for subnetting
• Debugging - Read hexadecimal memory dumps and convert addresses to decimal for analysis
• File permissions - Convert Unix permission values like 755 (octal) to understand the binary flag pattern
• Embedded systems - Work with register values and bit masks that alternate between hex and binary notation

• Four bases at once - See binary, octal, decimal, and hex representations simultaneously instead of converting one pair at a time
• Input validation - Invalid digits are caught immediately so you never get a wrong result from a typo
• Bit count included - Instantly know how many bits your number requires, useful for sizing data types
• Standard prefixes - Results include 0b, 0o, and 0x prefixes for unambiguous copy-pasting into code
• Free and instant - No installation, no sign-up — just type a number and see every base conversion immediately

What bases are supported?

The converter supports binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16) — the four numeral systems most commonly used in computing and digital electronics.

How do I enter hexadecimal numbers?

Use digits 0–9 and letters A–F (case-insensitive). For example, enter D6 or d6 with hexadecimal selected as the input base. The 0x prefix is optional.

Is there a maximum number size?

The converter handles numbers within standard JavaScript integer precision, which covers values up to 2⁵³ − 1 (about 9 quadrillion). For everyday computing tasks, this range is more than sufficient.

What happens if I enter an invalid digit?

The converter validates your input against the selected base. If you enter a digit that doesn't belong (like 2 in binary or G in hex), it will flag the error immediately rather than producing an incorrect result.

What does the bit count mean?

The bit count tells you how many binary digits are needed to represent the number. This is useful for determining whether a value fits in a byte (8 bits), a 16-bit word, a 32-bit integer, and so on.

Is this tool free?

Yes, the base converter is completely free with no usage limits or sign-up requirements.