Octal to Hex Converter Tool

Convert octal numbers to hexadecimal notation. Our tool validates input and explains the process. Handy for working with file permissions, older documentation, and digital systems using octal.

Octal to Hex Converter

Convert octal numbers (base-8) to hexadecimal (base-16)

Uppercase (A-F)

No prefix0x prefix

Octal Input

Hexadecimal Output

Common Octal to Hex Conversions

→ 0

→ 7

→ 8

→ F

→ 10

→ 1F

377

→ FF

400

→ 100

How it works

Enter an octal number (base-8, digits 0-7) in the input field. The converter transforms it to decimal as an intermediate step, then converts to hexadecimal (base-16) format.

The converter accepts octal numbers with or without prefixes (0o or leading 0). Invalid octal digits (8 or 9) are flagged as errors since octal only uses digits 0-7.

Results display instantly using BigInt for arbitrary precision. The hex output is shown in uppercase with optional "0x" prefix. Copy the result with a single click for use in code or documentation.

When You'd Actually Use This

File Permission Conversion

Convert Unix file permissions from octal (chmod values) to hex for documentation or analysis.

Legacy Code Migration

Update old codebases that use octal literals to modern hex notation.

System Administration

Translate between octal permission values and hex representations in security tools.

Computer Science Studies

Practice base conversion and understand relationships between number systems.

Data Interpretation

Read octal dumps or outputs from legacy systems and convert to more common hex format.

Debugging

Compare values when different tools display the same data in octal vs hex format.

What to Know Before Using

Valid octal digits: Only 0-7 are valid in octal. If you see 8 or 9, it's not octal - it might be decimal or a typo.

Octal prefixes: Traditional C uses leading 0 (0755), modern languages use 0o (0o755). Both are accepted.

Bit grouping: Octal groups binary by 3 bits, hex by 4 bits. Conversion requires regrouping bits or going through decimal.

Common octal values: File permissions like 644, 755, 777 are common octal values. Know what they represent.

Case convention: Hex output uses uppercase (A-F) by convention, though lowercase is equally valid.

Common Questions

What is 755 octal in hex?

755₈ = 1ED₁₆ (493 decimal). Common file permission: owner rwx, group r-x, other r-x.

How do I convert octal to hex manually?

Convert octal to decimal (multiply each digit by 8^position), then decimal to hex (divide by 16, collect remainders).

Why can't I use 8 or 9 in octal?

Octal is base-8, meaning it only has 8 digits (0-7). Just like decimal has 10 digits (0-9), binary has 2 (0-1).

What is 0o100 in hex?

0o100 (octal) = 64 (decimal) = 0x40 (hex). This is a common permission value (owner read+write only).

Can I convert decimal to hex?

Yes, but use the decimal-to-hex converter for that. This tool specifically handles octal-to-hex conversion.

What's 777 octal?

777₈ = 511 decimal = 0x1FF. In permissions, this means full read/write/execute for everyone (security risk).

How do I verify the conversion?

Convert back using hex-to-octal, or check via decimal intermediate. Both paths should give consistent results.

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Octal to Hex Converter Tool