Definition
As Bitcoin's computing power grew beyond what a single machine produces, larger SI-prefixed units became necessary to describe aggregated hashrate. A petahash per second (PH/s) is 1015 hashes, an exahash per second (EH/s) is 1018 hashes, and a zettahash per second (ZH/s) is 1021 hashes. Each step up the ladder multiplies the previous unit by one thousand, mirroring the standard metric prefixes.
Which unit describes what
The unit that fits depends on scale. A large mining farm or a small pool is typically measured in petahashes. The total Bitcoin network — the combined output of every honest miner on the planet — is now measured in exahashes, having crossed from petahash into exahash scale as ASIC deployment expanded. Zettahash is the next milestone the network is approaching, and the term is already used in forward projections of global mining capacity.
How the units chain together
These prefixes are purely arithmetic. One thousand terahashes equal one petahash; one thousand petahashes equal one exahash; one thousand exahashes equal one zettahash. This makes it easy to roll a fleet quoted in TH/s up to the unit appropriate for its size, then compare it against the published network hashrate.
Rising aggregate hashrate is the engine behind difficulty adjustment: as petahashes turn into exahashes, the protocol raises the bar to keep the average block interval near ten minutes. For the full unit family and conversion table, see hashrate units.
See network-scale hashrate in the live network vitals.
In Simple Terms
As Bitcoin’s computing power grew beyond what a single machine produces, larger SI-prefixed units became necessary to describe aggregated hashrate. A petahash per second (PH/s)…