Octal Encoder / Decoder

Convert between text, decimal, hex, and octal number representations.

Tested tool guide Tested browser tools Checked August 16, 2026

What Octal Encoder / Decoder does, with a checked example

Octal Encoder / Decoder translates text and whole-number values between base 8, base 10, and base 16 representations. It can expose the numeric value associated with a character or rewrite the same integer using a different set of digits. The important distinction is between a numeral and its value. The digits 10 represent ten in decimal but eight in octal. Octal permits only the digits 0 through 7, so an input containing 8 or 9 cannot be interpreted as a valid base-8 numeral.

Worked example

A concrete input and expected output from the current implementation.

Input

Expected output

With decimal selected as the input and octal as the output, 65 becomes 101. Checking the result in reverse gives 1 x 64 + 0 x 8 + 1 = 65.

How the result is produced

Interpreting octal

An octal numeral is positional: its rightmost digit counts ones, the next counts eights, then sixty-fours, and so on. Conversion preserves the underlying integer and changes only its written representation. Because the radix is eight, valid digits stop at 7. A displayed 101 in octal therefore represents a different magnitude from 101 in decimal or hexadecimal.

Relating text to numbers

When text is encoded, each character is associated with a numeric character value, which can then be written in decimal, hexadecimal, or octal. Decoding reverses that relationship. For the ASCII character A, the cross-base relationship is decimal 65, hexadecimal 41, and octal 101. When converting multiple characters, preserve the boundaries between their individual numeric values.

Good uses

Convert a decimal value from an ASCII table into octal while examining a legacy protocol, escape, or diagnostic dump.
Check the decimal or hexadecimal magnitude of an octal numeral found in source code, configuration, or permission-related notation.
Compare the text, decimal, hexadecimal, and octal forms of a character while debugging mismatched escapes or copied numeric data.

Limits and checks

An octal input containing 8 or 9 is invalid. If those digits appear, confirm that the source was not actually decimal or hexadecimal.
Bare digits do not identify their own base. The numeral 101 means decimal 101, octal 65, or hexadecimal 257 depending on the selected input representation.
Numeric character values do not by themselves specify a byte encoding. For non-ASCII text, confirm the character mapping before treating the numeric output as encoded file or network bytes.

Common questions

Is octal 101 the same value as decimal 101?

No. A numeral must be interpreted using its base. Octal 101 equals decimal 65 because 1 x 64 + 0 x 8 + 1 = 65. Decimal 101 converts to octal 145 because 1 x 64 + 4 x 8 + 5 = 101. Similar-looking digits do not imply equal values.

Can this tool explain the Unix permission value 755?

No. It can rewrite octal 755 as decimal 493 or hexadecimal 1ED, since 7 x 64 + 5 x 8 + 5 = 493. It does not interpret owner, group, read, write, or execute permissions. Use it to verify the numeric conversion, then consult Unix permission documentation for the operational meaning.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.