Number Base Converter
Binary, octal, decimal, hex.
Number Base Converter at a glance
Number Base Converter is a free online converter you can use right now to binary, octal, decimal, hex โ no account, no install and no usage limit. It runs entirely inside your browser, so whatever you enter stays on your own device.
- Price
- Free โ no trial, no paid tier, no watermark
- Sign-up
- Not required
- Where it runs
- In your browser โ nothing is uploaded to a server
- Works on
- Chrome, Safari, Firefox and Edge โ desktop, tablet and phone
- Category
- Converters
About Number Base Converter
Convert a number between binary, octal, decimal and hexadecimal, seeing all representations at once.
Hexadecimal exists because it maps cleanly onto binary: one hex digit is exactly four bits, so a byte is always two hex digits. That makes binary data compact and readable, which is why colour codes, memory addresses and byte dumps are all written in hex. Reading FF as 255 quickly becomes automatic once the four-bit mapping is clear.
Octal survives mainly because of Unix file permissions, where each digit represents exactly three bits โ read, write and execute. The 755 in chmod 755 is three octal digits: owner gets 7 (read, write, execute), group and others get 5 (read and execute). Understanding that mapping makes permission strings readable rather than memorised.
Binary is where bit flags and masks become legible. A permissions or options value stored as a single integer is genuinely opaque in decimal and immediately clear in binary, where each set bit is a distinct flag. This is why debugging bitwise operations almost always starts by converting the values to binary.
How to use Number Base Converter
- Enter your number in any base.
- Read the equivalent in binary, octal, decimal and hexadecimal.
- Use the binary view to inspect individual bits when debugging flags.
Frequently asked questions
Why is hexadecimal used so widely in programming?
Because one hex digit is exactly four bits, so a byte is always two hex digits. That makes binary data compact and readable, which is why colour codes, memory addresses and byte values all use it.
Why are Unix permissions written in octal?
Because permissions come in groups of three bits โ read, write, execute โ and one octal digit is exactly three bits. So 755 gives the owner read, write and execute, and group and others read and execute.
When is binary actually useful?
For bit flags and masks. An options value stored as one integer is opaque in decimal and obvious in binary, where each set bit is a separate flag. Debugging bitwise operations usually starts with a binary conversion.
What do the 0x and 0b prefixes mean?
They mark the base in most programming languages โ 0x for hexadecimal, 0b for binary and a leading 0 or 0o for octal. Without a prefix, a number is assumed decimal.