Kilohertz to gigahertz: how a clock rate crosses six decades
What this conversion does
It divides by a million, taking a figure quoted in thousands and restating it in billions. The two units are far apart enough that the answer is usually a small decimal: a processor at 3,500,000 kHz runs at 3.5 GHz. Converting between them is mostly a way of checking that a datasheet and a measurement agree, since one is usually written in each unit.
From the first microprocessor to now
The earliest commercial processors ran at a few hundred kilohertz, and a modern one runs thousands of times faster. Both ends of that history are still quoted in their original units: a legacy system is described in kilohertz while its replacement is described in gigahertz. Converting is what makes the comparison meaningful rather than a comparison of two different-looking numbers.
Kilohertz to gigahertz conversion table
Clock rates old and new, in both units, showing how the same progression looks from either side of the decimal point.
| Kilohertz (kHz) | Gigahertz (GHz) |
|---|---|
| 1 | 0.000001 |
| 10 | 0.00001 |
| 100 | 0.0001 |
| 530 | 0.00053 |
| 1000 | 0.001 |
| 1700 | 0.0017 |
Why the answer so often has leading zeroes
A gigahertz is a million kilohertz, so any frequency below a million kilohertz is less than one gigahertz. Since most kilohertz figures in computing are in the hundreds or thousands, the answer usually begins with a zero and carries several decimal places. That is not an error, it is the unit being large relative to the value.
Check the order of magnitude first
Before converting, ask whether the answer should be near one or near a thousand. A clock quoted at 800,000 kHz is 0.8 GHz, and one quoted at 3,500,000 kHz is 3.5 GHz. The leading digit tells you immediately whether you have slipped by a factor of a thousand.
Frequently asked questions
How many kilohertz are in one gigahertz?
One million. The prefix steps up twice from kilohertz, first to megahertz and then to gigahertz, and each step multiplies by a thousand. So 1 GHz is 1000 MHz and 1,000,000 kHz.
How do I convert a processor clock from kilohertz to gigahertz?
Divide the kilohertz figure by a million. A 3,500,000 kHz clock is 3.5 GHz. If the number you start with is below a million, the answer will be less than one gigahertz and will need a leading zero.
Why do old computers list clock speed in kilohertz?
Because that is what they ran at. Early microprocessors ran at a few hundred kilohertz to a few megahertz, so kilohertz was the natural unit. Modern processors run in gigahertz, and converting the old figures is the only way to compare them directly.
Is a gigahertz the same as a billion cycles per second?
Yes. One hertz is one cycle per second, so one gigahertz is a billion cycles per second. A 3.5 GHz processor therefore completes three and a half billion clock cycles every second it is running.
Can a frequency be converted the other way as well?
Yes. The conversion is a single multiplication by a power of ten, so it reverses exactly. A separate page handles gigahertz to kilohertz, and because the factor is a power of ten the round trip returns the original number with no drift.