Octal to Hexadecimal Converter
Convert octal (base-8) numbers to hexadecimal (base-16) format for memory addresses, color codes, and modern programming, from Unix permission values and legacy octal data.
Conversion Options
Conversion Process:
Octal → Decimal → Hexadecimal
Example: 0o377 → 0xFF
Unix permissions: 0o777 → 0x1FF (rwxrwxrwx)
Recommended Settings
Pro Tips
- •Hexadecimal (base-16) aligns perfectly with byte boundaries, making it the modern standard over octal
- •The conversion goes through decimal as an intermediate step using BigInt, so it works correctly for very large octal values
- •0o and leading-zero prefixes are automatically stripped from the input
- •Grouping in 2s mirrors byte boundaries; grouping in 4s mirrors 16-bit word boundaries
Most Popular
Most users add the 0x prefix and keep lowercase letters for standard hex notation
When to Use This Tool
Convert Unix octal permission values (like 0o755) into hexadecimal when working with APIs, tools, or documentation that expect permission masks in hex.
Translate octal-based memory addresses, device numbers, or configuration values from older systems and documentation into the hexadecimal notation used by modern tools.
Convert octal literals or values found in legacy C code, shell scripts, or PDP-era documentation into hex for use in modern debuggers, memory viewers, or source code.
Re-express octal-grouped binary data (3 bits per digit) as hexadecimal (4 bits per digit) for compatibility with byte-oriented tools and hardware documentation.
How It Works
Parse input octal strings (with or without 0o or leading-zero prefixes)
Strip prefixes and validate that only digits 0-7 remain
Convert octal to decimal using BigInt for accurate results with very large numbers
Convert the decimal value to hexadecimal using base-16 positional notation
Apply formatting: uppercase letters, digit grouping, and the 0x prefix if enabled
Handle multiple values with configurable output delimiters
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Pure JavaScript with BigInt for optimal performance on modern browsers.
Secure
No data collection, no tracking, no sign-up required.
Frequently Asked Questions
How does octal convert to hexadecimal?
The conversion goes through decimal as an intermediate step: octal → decimal → hexadecimal. There's no direct digit-for-digit mapping because octal digits represent 3 bits while hex digits represent 4 bits. For example, 0o377 (octal) → 255 (decimal) → 0xFF (hex).
Why convert Unix permissions to hexadecimal?
While chmod and Unix tooling use octal (like 755), some APIs, programming languages, and low-level tools represent permission masks or file mode bits as hexadecimal values instead. Converting lets you work with either representation as needed.
What happens to 0o or leading-zero prefixes?
Both the modern 0o prefix (e.g., 0o755) and the classic C-style leading zero (e.g., 0755) are automatically stripped before conversion, so you can paste octal values in either style.
Can this handle very large octal numbers?
Yes. The conversion uses JavaScript's BigInt for the octal-to-decimal step, so very large octal values convert to hexadecimal exactly, without the precision loss that regular floating-point numbers would introduce.
What's the difference between 2-digit and 4-digit grouping?
2-digit grouping mirrors byte boundaries (each pair of hex digits is one byte), which is useful for memory dumps and binary data. 4-digit grouping mirrors 16-bit word boundaries, common when working with larger registers or addresses.