zettabit

A zettabit (symbol Zb) is a unit of information equal to 10^21 bits. It is derived from the SI prefix zetta- (10^21) combined with the bit unit (b). For data rate, it is commonly written as Zbps when used per second.

One zettabit equals 1,000,000,000,000,000,000,000 bits. In bytes, this is 1.25 × 10^20 bytes, or about 125 exabytes.

In practice, zettabits are rarely used; larger measures such as zettabytes (bytes) or exabytes are more common. Zettabits appear mainly in theoretical discussions of global bandwidth or very long-term data accumulation.

The zetta prefix is part of the International System of Units (SI). Because a zettabit denotes a quantity of bits, it is important to specify the unit (bits versus bytes) when communicating about large-scale data.