Octal to Hex Converter

Convert an octal number into its uppercase hexadecimal form for cross-base arithmetic and register inspection.

Quick Converter

Use a compact field for small conversion and calculation tools.

Input

Focused controls for small conversions and calculations.

Value

Results

Readable cards for unit-heavy output, with raw output kept for special cases.

Enter a value above or tap a sample to see structured results.

What is Octal to Hex Converter

Last reviewed: April 18, 2026

Octal (base 8) represents numbers with digits 0-7 and is still common in Unix file permissions and some legacy systems.

Octal to Hex Converter reads an octal number (with or without the 0o prefix) and outputs the uppercase hex representation.

This is particularly handy when working with Unix file modes, network protocols that express values in octal, or legacy documentation that mixes octal and hex notations.

Why use it

Translate Unix file modes into hex bitmasks.
Cross-check documentation that presents the same value in multiple bases.
Prepare octal input for hex-only systems.
Verify manual base conversions during debugging.
Teach octal/hex relationships through binary grouping.

Features

Accepts 0o prefix or plain octal
Uppercase hex output
Clear error messages
Client-side conversion
Copy-ready result

How to use Octal to Hex Converter

Paste the octal. Enter an octal number in the input panel.
Read the hex. The uppercase hex equivalent appears in the output.
Copy it. Copy the hex into your code or report.

Example (before/after)

Octal input

Hex output (uppercase)

1ED

Common errors

Non-octal digits

Digits 8 and 9 do not exist in octal.

Fix: Correct the input to use only 0-7.

Large values

Numbers beyond the safe integer range lose precision.

Fix: Use a BigInt-capable utility for values above 2^53 - 1.

Expecting lowercase hex

Some tools want lowercase, but this tool returns uppercase by default.

Fix: Lowercase the result manually if your downstream needs it.

FAQ

Can I include the 0o prefix?

Yes. The tool strips it before parsing.

Why uppercase hex?

Uppercase is the common default in documentation and many APIs; lowercase is easy to convert downstream.

Does it support very large values?

Up to 2^53 - 1 due to JavaScript number precision.

Is it performed locally?

Yes, client-side only.

What happens with an empty input?

The tool shows a helpful error.

How do I reverse the conversion?

Use the Hex to Octal tool.

Related tools

Round-trip through bases and inspect other cross-base utilities. You can also browse the full Unit Converters category for more options.

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