The gigahertz is a unit of frequency equal to one thousand million hertz. Its symbol is GHz. It is the range of modern wireless communication and of the clock inside every current computer, and almost nothing in it was in everyday use before the 1990s.
Wi-Fi occupies two main bands, at 2.4 and 5 gigahertz, with a newer band near 6. The 2.4 gigahertz band is crowded because it is licence-free almost everywhere and shared with Bluetooth, cordless phones and microwave ovens, which operate at 2.45 gigahertz because water molecules absorb energy efficiently there. The 5 gigahertz band offers more channels and higher rates but is absorbed more strongly by walls, so it covers a smaller area.
Mobile telephony spans the range. Earlier generations used bands below 1 gigahertz for their long reach into buildings and across countryside, while newer allocations at 1.8, 2.6 and 3.5 gigahertz carry more data over shorter distances. The higher a frequency, the more bandwidth is available and the less it penetrates, and every generation of network design is a negotiation between those two facts.
Computer clock speeds crossed into gigahertz around the year 2000 and stalled near four a few years later. The limit is thermal: power dissipation rises steeply with frequency, and beyond about four gigahertz a conventional silicon processor cannot shed the heat. Performance gains since then have come from adding cores, widening instruction issue and improving memory hierarchies rather than from raising the clock.
Satellite links, radar and radio astronomy all work here. Weather radar typically runs between 2.7 and 5.6 gigahertz, air traffic control radar in similar bands, and the microwave background radiation that fills the universe peaks near 160 gigahertz, well above the range of terrestrial communication.
Millimetre-wave systems at 24 gigahertz and above are used for automotive collision-avoidance radar and for the highest-capacity mobile network bands. Their very short wavelengths allow small antennas and enormous data rates but are blocked by almost anything, including rain and foliage.
One gigahertz equals one thousand million hertz, 1000 megahertz, or 0.001 terahertz.
| Unit | Symbol | 1 Gigahertz equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Nanohertz | nHz | 1 × 1018 nHz | 1 × 10-18 GHz | Gigahertz to Nanohertz |
| Microhertz | µHz | 1 × 1015 µHz | 1 × 10-15 GHz | Gigahertz to Microhertz |
| Millihertz | mHz | 1000000000000 mHz | 1 × 10-12 GHz | Gigahertz to Millihertz |
| Hertz | Hz | 1000000000 Hz | 0.000000001 GHz | Gigahertz to Hertz |
| Kilohertz | kHz | 1000000 kHz | 0.000001 GHz | Gigahertz to Kilohertz |
| Megahertz | MHz | 1000 MHz | 0.001 GHz | Gigahertz to Megahertz |
| Terahertz | THz | 0.001 THz | 1000 GHz | Gigahertz to Terahertz |