CRC Calculator
CRC-8 / 16 / 32 checksum — text or hex input, parameters built in.
What it does: Computes the CRC checksum of data using the selected standard.
When to use it: Working on communication protocols, firmware checksums, or Modbus debugging.
MEANS The sender and receiver must use the same CRC standard for the checksums to match.
No history yet. Each calculation is automatically saved to this device.
How to use the CRC calculator
Choose the input and standard.
- 01
Choose the input mode
Text (bytes taken as UTF-8) or hexadecimal bytes (such as
31 32 33). - 02
Choose the CRC standard
CRC-8 / CRC-16-CCITT / CRC-16-MODBUS / CRC-32, with parameters built in.
- 03
Read the checksum
Get the CRC in hexadecimal and decimal.
CRC standard parameters
The check value of "123456789" is used to verify implementation correctness.
| Standard | Polynomial | Init | refin/out | check(123456789) |
|---|---|---|---|---|
| CRC-8 | 0x7 | 0x0 | No | 0xF4 |
| CRC-16/CCITT-FALSE | 0x1021 | 0xFFFF | No | 0x29B1 |
| CRC-16/MODBUS | 0x8005 | 0xFFFF | Yes | 0x4B37 |
| CRC-32 | 0x4C11DB7 | 0xFFFFFFFF | Yes | 0xCBF43926 |
RevEng CRC catalogue / crccalc.com.
Common questions, answered in 3 minutes
Can a CRC correct errors?
No, it can only detect them. A CRC is used to find bit errors in transmission/storage; for error correction use Hamming codes and the like.
Why do different standards give different results for the same data?
A CRC is determined by parameters such as the polynomial, init value, whether to reflect, and the XOR output; different standards have different parameters, so the results naturally differ. The sender and receiver must use the same standard.
What are refin/refout?
Bit reflection: many serial protocols send the least significant bit first, so the input bytes and the final CRC are bit-reversed. MODBUS and CRC-32 both use reflection.
How do you confirm the implementation is correct?
Compute over the standard string "123456789"; the result should equal that standard's check value (see the table above). This tool has passed the check verification for all four standards.
Standards and sources referenced by this tool
| Item | Value / Formula | Source |
|---|---|---|
| CRC algorithm | Parameterized bitwise CRC | RevEng CRC catalogue |
Parameters and check values from the RevEng CRC catalogue; the implementation has passed the 123456789 check, no external API.