Hex CRC8 Calculator
Compute a CRC8 checksum (polynomial 0x07) from hex byte input — a lightweight error-detection code used in small embedded protocols.
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: Cyclic redundancy check — Wikipedia
How CRC8 Is Computed
CRC8 processes the input one byte at a time using a table derived from its generator polynomial (0x07), starting from an initial value of 0x00 with no bit reflection — the simplest of the common CRC widths, and small enough to reason through by hand for a single byte.
CRC8 Test Vector, Verified
CRC-8("123456789") = 0xF4
CRC8(0x313233343536373839) = 0xF4
Input bytes: "123456789" (9 ASCII bytes) Run CRC-8 (poly 0x07) over all 9 bytes Result: 0xF4 (the official check value)
| Step | Description | Result |
|---|---|---|
| Encode input as bytes | "123456789" -> 0x313233343536373839 (9 bytes) | 9 bytes |
| Run CRC-8 | process each byte through the table-driven update, starting at 0x00 | running 8-bit value |
0xF4 is the standard published check value for this CRC-8 variant — a correct implementation reproduces this exact result for this exact input.
Where CRC8 Actually Comes Up
Verifying an SMBus Packet Error Code
SMBus (a variant of I2C used in system management) appends a single-byte packet error code computed with this CRC8 variant, which devices recompute to detect a corrupted transfer.
packet bytes + PEC trailer
Protecting a Short Sensor Reading
Small embedded sensors that report just a few bytes at a time often use CRC8 rather than a wider CRC, since the overhead of a larger check value isn't worth it for such a short message.
3-byte reading + 1-byte CRC8
Sanity-Checking a Custom CRC8 Implementation
Running the standard "123456789" test vector through your own CRC8 code and comparing against 0xF4 catches a wrong polynomial or initial value before it reaches production firmware.
CRC8("123456789") == 0xF4
Why Use This Calculator Instead of Doing It by Hand
- Verified against a standard CRC-8 check value before shipping
- Table-driven implementation computes instantly even on longer byte sequences
- Runs entirely in your browser — nothing you type gets sent anywhere
- Accepts hex byte input directly, matching how embedded protocol payloads are usually represented
Limitations
- Computes the CRC-8/SMBUS variant (poly 0x07, no reflection) specifically — other CRC8 flavors (CRC-8/MAXIM, CRC-8/ITU) use different parameters and will not match.
- Input is treated as raw hex bytes — an odd number of hex digits gets a leading zero nibble added first.
Frequently Asked Questions
Which CRC8 variant does this calculator use?
CRC-8/SMBUS (polynomial 0x07, initial value 0x00, no bit reflection) — one of the most common CRC8 variants, used for the SMBus packet error code among other small protocols.
How do I verify this calculator computes CRC8 correctly?
Enter 313233343536373839 (the hex bytes for the ASCII string "123456789") — the standard check value for this CRC8 variant on that input is 0xF4, which this calculator reproduces exactly.
Why use CRC8 instead of CRC16 or CRC32?
CRC8 is cheaper to compute and needs less storage (just 1 byte), making it a practical choice for small embedded protocols or short messages where a wider CRC would be overkill for the amount of data being protected.
Is a 1-byte CRC good enough for reliable error detection?
It catches most common errors (single-bit flips, many burst errors) but has a much smaller space of possible values than CRC16 or CRC32, so it's less suited to protecting large amounts of data where undetected corruption is costlier.