Frequency Converter

Frequency counts how many times something repeats each second. The SI unit is the hertz (Hz): one hertz is one cycle per second. What makes frequency remarkable is its reach. The same unit describes a slow heartbeat, a musical note, a radio carrier, and a beam of light, spanning more than fifteen orders of magnitude.

Metric prefixes:

• 1 kHz = 1,000 Hz
• 1 MHz = 1,000,000 Hz
• 1 GHz = 1,000,000,000 Hz
• 1 THz = 1,000,000,000,000 Hz

Frequencies you can place:

• Human hearing: 20 Hz to 20 kHz
• FM radio: 88–108 MHz
• Wi-Fi (2.4 GHz band): 2,400 MHz
• Visible light: 430–770 THz

Frequency and period are two views of one thing. The period is one divided by the frequency, so a 100 Hz signal repeats every 0.01 seconds. If someone hands you a time per cycle and you need a rate, just flip it.

A frequent snag is angular frequency, written as omega and measured in radians per second. It runs through physics and signal processing and equals 2π times the frequency in hertz, so 50 Hz mains works out to about 314 rad/s. Both describe the same oscillation: one counts whole cycles, the other counts radians of phase. Check which one a formula expects before you plug numbers in.

RPM is a frequency too. Anything that spins has a rate, and mechanical work quotes it per minute rather than per second, so 3,000 RPM is 50 Hz and an engine at 6,000 RPM is turning at 100 Hz. The RPM field above converts straight across, which saves the division by 60 that people get backwards about half the time.

For anything electromagnetic there is a second number worth having: the wavelength. Divide the speed of light by the frequency and you get the physical size of one wave, which is what actually decides how long an antenna has to be and why a 2.4 GHz Wi-Fi wave, at 12.5 cm, passes through a doorway that would stop light. The converter prints it alongside the period for that reason.