Rust Integer to Hex Converter
Convert a Rust integer to its hexadecimal string form — the same conversion the {:x} format specifier performs.
Built by
Swapnil SanghviFull-Stack Web Developer & WordPress Developer
Swapnil Sanghvi is a full-stack web and WordPress developer, UI designer, and full-time freelancer who builds and maintains Hex Calculator.
Further reading: hex — Stack Overflow
How Rust Converts an Integer to Hex
The {:x} format specifier converts an integer to base 16 using lowercase digits, with no prefix and no padding unless you add the # flag or a width specifier. This works for any of Rust's integer types (u8, i32, u64, and so on).
Where Rust Integer to Hex Actually Comes Up
Formatting a Value for Debug Output
Printing a computed integer — a hash, a pointer-like value, or a bitmask — in hex often makes it easier to read and compare in debug output or logs.
println!("{:#x}", value)
Building a Hex-Encoded String Representation
Converting a numeric ID or byte value to its hex form as part of building a formatted string, such as a hex dump or a compact identifier.
format!("{:02x}", byte)
Checking Expected Output Against a Reference Value
Verifying what a Rust program's hex formatting should produce for a given integer, useful when writing tests or reference documentation.
confirm format!("{:x}", 255) == "ff"
Why Use This Calculator Instead of Doing It by Hand
- Matches the digit output of Rust's {:x} format specifier
- Runs entirely in your browser — nothing you type gets sent anywhere
- Saves manually converting and formatting the output
- Useful for checking expected output before writing test assertions
Limitations
- Adds a 0x prefix and uses uppercase digits — Rust's {:x} returns lowercase digits with no prefix by default (add # for the prefix, {:X} for uppercase).
- Doesn't zero-pad to a fixed width — add a width specifier in your format string yourself if you need that.
Frequently Asked Questions
How do I convert an integer to hex in Rust?
Use the {:x} format specifier — format!("{:x}", 255) returns "ff", lowercase with no prefix. Use {:X} for uppercase digits instead.
How do I include the 0x prefix in the output?
Add the # flag — format!("{:#x}", 255) returns "0xff", including the prefix automatically.
How do I zero-pad the result to a fixed width?
Combine a width specifier with zero-padding, like format!("{:08x}", value), which pads to 8 digits with leading zeros.
How do I parse a hex string back into an integer in Rust?
Use i32::from_str_radix(hex_str, 16) (or the equivalent for your target integer type) — the counterpart for parsing a hex string into a typed integer.