Gigahashes/sec (Gigahashes per second, abbreviated GH/s) is a unit measuring hashing speed, that is, the number of attempts to compute a valid hash that a device makes per second. One gigahash equals a billion hash operations. In essence, this indicator reflects the "performance" of mining hardware in the same way that gigahertz characterize a processor's clock speed.

The higher a device's hashrate, the greater its chances of finding a suitable block and earning a reward in a network running on the Proof-of-Work algorithm. The units of measurement scale up as hardware power grows:

• kilohash/s (KH/s) — thousands of operations;
• megahash/s (MH/s) — millions;
• gigahash/s (GH/s) — billions;
• terahash/s (TH/s) and higher — trillions and more.

At the dawn of mining, graphics cards with figures in megahashes were enough. With the advent of specialized ASIC devices, performance grew by orders of magnitude, and today industrial hardware is more often rated in terahashes and petahashes. Gigahashes, meanwhile, remain a convenient intermediate unit for comparison.