One gigahertz is exactly 1,000 megahertz. This is the pair of modern computing and wireless networking, and it is where processor clock speeds stopped climbing about twenty years ago.
About the units
A gigahertz is 10⁹ cycles per second. Processor clock speeds crossed 1 GHz in 2000 and reached roughly 4 GHz by 2005, then stopped — not because faster switching is impossible but because power consumption rises steeply with frequency and the heat becomes unmanageable. Performance since then has come from more cores and better architecture rather than higher clocks. In radio, the gigahertz range covers Wi-Fi at 2.4 and 5 GHz, mobile networks from 700 MHz to 3.5 GHz for 4G and 5G, and satellite links above that.
The exact factor
The factor is exactly 1,000. The wavelength relationship continues from the radio bands: at 1 GHz the wavelength is 30 centimetres, at 2.4 GHz it is 12.5 cm, and at 60 GHz it is 5 mm. That progression explains the behaviour of wireless networks — 2.4 GHz passes through walls reasonably well, 5 GHz less so, and millimetre-wave 5G at 26 GHz is stopped by a hand. Higher frequency carries more data and travels less far, and that trade-off is fixed by physics rather than engineering.
Where you meet this conversion
Computing and wireless. Processor and memory clock speeds, bus frequencies and graphics card specifications are all in gigahertz while their subsystems are described in megahertz. Wi-Fi band selection, mobile network planning and radar all work in this range. Microwave ovens operate at 2.45 GHz, chosen because it is an unlicensed band rather than because water resonates there — a common myth. Satellite television downlinks are at 10 to 12 GHz.