Frequency converter

What it's for

The hertz counts how many times something repeats in a second, and the same unit describes phenomena that seem worlds apart: musical notes, an engine's revolutions, a screen's refresh, radio stations, a heartbeat. Converting is needed because every field writes it its own way — some in kilohertz, some in revolutions per minute, some in beats per minute.

The conversions you actually need

From revolutions per minute to hertz you divide by 60: an engine at 3000 rpm turns at 50 Hz, and a vinyl record at 33 rpm sits at 0.55 Hz. The same holds for the beats per minute of music and of the heart: 120 BPM is 2 Hz. The other way round you multiply by 60, and that's the sum you need when a spec sheet talks in hertz and the rev counter in revolutions.

For the multiples: 1 kHz is a thousand Hz, 1 MHz a million, 1 GHz a billion. Human hearing runs roughly from 20 Hz to 20 kHz; FM radio sits between 87.5 and 108 MHz; WiFi works at 2.4 and 5 GHz.

The hertz that don't talk to each other

They're all hertz, but they measure different things, and mixing them up is common. A processor's gigahertz says how many clock cycles it does a second, not how fast it is: a recent 3 GHz chip does far more work per cycle than an old one at the same frequency, which is why comparing gigahertz across generations means nothing.

A screen's hertz is the frames per second it can show (60, 120, 144), and it's about smoothness. The 50 Hz of the mains is the alternating current's reversals, and it's 60 in America: that's why certain old imported appliances run faster or slower.

Nearby tools

For musical tempo, measured by tapping along, there is BPM counter; for the match between note and frequency Note, frequency and MIDI and to tune up Guitar tuner. For time units there is Time converter.