How to use the CRC Calculator
- 1. Pick a modeCalculate a CRC, check a received codeword, or CRC-32 of text.
- 2. Enter the bitsData bits and a generator like 1011, or pick a standard one.
- 3. CalculateSee the XOR steps, the remainder and the codeword to send.
How a CRC is calculated
A CRC (cyclic redundancy check) detects accidental changes to data, and is used in Ethernet, Wi-Fi, ZIP and PNG files. The sender and receiver agree on a generator polynomial, written as bits: x³ + x + 1 is 1011.
- Append as many 0s to the data as the generator's degree (its length minus 1).
- Divide using modulo-2 division: wherever the leading bit is 1, XOR the generator underneath. There are no carries or borrows.
- The remainder is the CRC. Replace the appended 0s with it and send the result.
The receiver divides the whole codeword by the same generator. A remainder of all 0s means no error was detected; anything else means some bits changed. The tool lists each XOR step, so you can follow it like the working in a networking exam.
Worked example
Data 11010011101100 with generator 1011 (degree 3): append 000 to get 11010011101100000, then divide. The first XOR is 1101 ⊕ 1011 = 0110, and so on along the row. The remainder is 100, so you transmit 11010011101100100.
Switch to Check a received codeword and enter that codeword: the remainder is 000, so no error is detected. Flip any one bit and the remainder becomes non-zero.
The CRC-32 mode uses the same polynomial and settings as ZIP, PNG and Ethernet. For the text 123456789 it gives CBF43926, the official check value for CRC-32, so you can confirm the tool against any other implementation.
Frequently asked questions
Can a CRC miss errors?
Rarely. A CRC with an r-bit remainder catches all single-bit errors, all bursts up to r bits, and most others, but it is not a security check; use a cryptographic hash for that.
Why does the generator start and end with 1?
The leading 1 sets the degree, and a trailing 1 is needed to catch all single-bit errors.
Is CRC the same as a checksum?
It's a kind of checksum, but much stronger than simply adding up the bytes.
Is the crc calculator free to use?
Yes, the crc calculator is free and costs nothing. Your first CRC shows a short form for your name and WhatsApp number one time; once that's done, this tool and every other Uncodemy tool open with no form.