What is a parity bit?

A parity bit is an extra bit added to a group of data bits so the total number of 1 bits is either always even (even parity) or always odd (odd parity). It is the simplest form of error detection used in serial links and memory.

What does even parity versus odd parity mean?

Even parity sets the extra bit so the count of 1 bits including the parity bit is even. Odd parity sets it so that count is odd. The two schemes detect the same single-bit errors but disagree on the parity bit value.

Can parity detect every error?

No. A single parity bit catches any odd number of flipped bits but misses an even number of flips, because two errors cancel out in the count. For stronger detection you need CRCs or Hamming codes.

How is the parity computed here?

The tool counts the set bits using arbitrary-precision arithmetic, then takes that count modulo 2. An even result means even parity, an odd result means odd parity, regardless of how large the number is.

Where is parity still used today?

Parity remains common in UART serial communication, older ECC memory, RAID systems, and many embedded protocols where a cheap single-bit check is enough to flag corruption and request a retransmission.

Bit Parity Calculator

Parity is the oldest and cheapest error-detection trick in computing: count the 1 bits and remember whether that count is even or odd. This tool tells you the parity of any integer and, for both the even-parity and odd-parity conventions, exactly which bit you would append to a frame.

How it works

The tool counts the set bits in your value and takes that count modulo 2:

ones        = number of 1 bits in the value
data parity = ones mod 2        // 0 = even, 1 = odd
even bit    = data parity       // appended, keeps the total even
odd bit     = 1 − data parity   // appended, keeps the total odd

For even parity the appended bit makes the overall number of 1 bits even; for odd parity it makes the overall count odd. A receiver recomputes parity over the data plus the parity bit and flags an error if it does not match the agreed scheme. A single flipped bit always changes the count, so it is always caught.

Example and notes

The byte 182 is 10110110, which contains five 1 bits — an odd number, so its data parity is odd. To transmit it under even parity you would append a 1 (making six 1 bits, even); under odd parity you would append a 0 (leaving five, odd). Parity cannot locate or correct the error, only detect it, and it misses errors that flip an even number of bits — that is why robust systems layer CRCs or Hamming codes on top.