Binary to Octal Converter

Q: Can I convert many binary numbers at once?

Yes. Put one number per line and every line is converted, with the results lined up against the input. A line that is not a valid binary number is left blank and reported by line number, so one typo does not stop the rest.

Q: How do you convert binary to octal?

Split the binary into groups of three from the right, padding the leftmost group with zeros, and replace each group with its value 0–7. 1011 → 001 011 → 13.

Q: Why are file permissions written in octal?

Unix permissions are nine bits — read, write and execute for owner, group and others. Three bits per group means each group is exactly one octal digit, so 755 reads directly as rwx, r-x, r-x.

Q: Is octal still used anywhere else?

Rarely. Besides permissions it appears in some older systems, in escape sequences like \033, and in aviation transponder codes. Hex has replaced it almost everywhere else.

Convert binary to octal instantly — three bits per octal digit — with Unix permission readings for small values.

Binary

Octal

Group digits Add 0x / 0b / 0o prefix Uppercase hex Pad to whole bytes

What It Does

This converter turns binary into octal. Because 8 is 2^3, every three bits from the right make one octal digit, so the conversion is a regrouping rather than arithmetic. Octal survives mostly in Unix file permissions, where each digit is one rwx triple — so for small values the tool also shows the permission string.

When to Use It

You know which permission bits you want and need the octal mode for chmod.
You are reading old documentation or hardware that uses octal.
You are practising base conversion by grouping bits.
You want several binary values converted at once.

Worked Examples

111101101

Groups 111 101 101 give 755 — rwxr-xr-x, the usual mode for executables and directories.

110100100

110 100 100 is 644 — rw-r--r--, the usual mode for ordinary files.

1010

Padded to 001 010, which is 12 in octal (ten in decimal).

Features

Converts as you type

Bulk conversion one number per line

Exact for numbers of any size

Digit grouping and 0x/0b/0o prefixes

Swap direction in one click

Explains bit width and two's complement

How to Use

1. Type or paste a binary number — or a list, one per line. 2. The octal value appears alongside, line for line. 3. Use the options to group digits or add a prefix, and the swap button to convert the other way.

Common Mistakes

Converting a number through a JavaScript Number. Above 9,007,199,254,740,991 it silently rounds, so the last digits come out wrong. This tool uses BigInt and stays exact at any size.
Forgetting that the same digits mean different values in different bases. 10 is ten in decimal, two in binary, eight in octal and sixteen in hex — always label which base a value is in.
Treating a minus sign as how a computer stores a negative number. Hardware uses two's complement, so a negative value's bit pattern looks nothing like its positive counterpart.

Frequently Asked Questions

Can I convert many binary numbers at once?

How do you convert binary to octal?

Why are file permissions written in octal?

Is octal still used anywhere else?

Conversion runs in your browser with exact integer arithmetic. Nothing is uploaded.