In computing, the least significant bit (LSB) is the bit position in a binary number having the value of 1. The LSB is sometimes referred to as the right-most bit. By contrast, the least significant digit of a decimal number is the digit in the ones (right-most) position.

In referencing specific bits within a binary number, each bit is assigned a bit number, ranging from zero to n (depending on the number of bits in the number.) Bit zero may refer to the LSB or the MSB, depending on the endianness.

By extension, the least significant bits (plural) are the bits of the number closest to, and including, the LSB.

The least significant bits have the useful property of changing rapidly if the number changes even slightly. For example, if 1 (binary 00000001) is added to 3 (binary 00000011), the result will be 4 (binary 00000100) and three of the least significant bits will change (011 to 100). By contrast, the three most significant bits stay unchanged (000 to 000).

Least significant bits are frequently employed in pseudorandom number generators, hash functions and checksums.

See also

• Most significant bit
• Binary numeral system
• Signed number representations
• Two's complement