CRC-16 Calculator

Use the Input text panel on the left to calculate a CRC-16 checksum. The output appears in the CRC-16 Result panel on the right.

1. Enter or paste the characters you want to check into Input text.
2. Choose Input Encoding. Keep UTF-8 for ordinary text unless your source uses another encoding.
3. Under Separator, select Hex (lower), Hex (UPPER), or Base64 to control how the result is displayed.
4. Leave Auto / Live enabled to see the checksum update as you type, or click Run to calculate it manually.
5. Read the value in CRC-16 Result. Click Copy to reuse it, or Clear to remove the input.

For a quick check, enter 123456789 with UTF-8 input and Hex (lower) output. The default CRC-16/ARC model returns bb3d (or BB3D in uppercase).

How CRC-16/ARC Works

CRC-16 means cyclic redundancy check with a 16-bit result. The algorithm processes a sequence of bytes to produce a short value that can help identify accidental changes in stored or transmitted data. A full CRC-16 checksum is typically written as four hexadecimal digits.

The default CRC-16/ARC variant uses polynomial 0x8005, initial value 0x0000, reflected input and output, and final XOR 0x0000. It is also commonly called CRC-IBM or CRC-16/LHA.

CRC-16/ARC vs. MODBUS and CCITT-FALSE

Not every CRC16 implementation uses the same parameters. For the ASCII test string 123456789, CRC-16/ARC gives BB3D, while CRC-16/MODBUS gives 4B37 and CRC-16/CCITT-FALSE (CRC-16/IBM-3740) gives 29B1. A result that differs from another calculator does not necessarily indicate an error: first confirm the model and the exact bytes being checked.

Text Encoding and CRC-16 Output Formats

A CRC is calculated from bytes, not directly from the characters you see. The Input Encoding setting determines how the text is represented before calculation. Under UTF-8, entering 41 checks two characters, not the single hexadecimal byte 0x41. Whitespace and line breaks also count as input.

The options labeled Separator affect the displayed checksum: Hex (lower) uses a–f, Hex (UPPER) uses A–F, and Base64 uses Base64 notation. Changing the output format does not change the CRC value itself.

When a CRC16 Checksum Is Useful

• Protocol debugging: compare a calculated checksum with an expected value after confirming the same CRC variant and input bytes.
• Test vectors: produce repeatable reference values for unit tests and parser checks.
• Accidental-change detection: compare checksums for copied configuration strings or text payloads.

Important: CRC-16 is an error-detection code, not encryption or a cryptographic hash. It should not be used to store passwords or prove that data has not been deliberately altered.