21 hertz (21 Hz)

21 hertz equals 2.1 × 10-8 gigahertz, 0.000021 megahertz, 0.021 kilohertz and 1,260 revolutions per minute.

21 hertz = 2.1 × 10-8 gigahertz

What 21 hertz means in practice

21 hertz sits between the lowest note humans can hear (20 Hz) and European mains electricity (50 Hz).

  • A resting human heartbeat: 1.2 Hz
  • The lowest note humans can hear: 20 Hz
  • European mains electricity: 50 Hz
  • North American mains electricity: 60 Hz
  • Middle C on a piano: 261.63 Hz
  • The tuning note A4: 440 Hz
  • The highest note humans can hear: 20,000 Hz
  • AM radio: 1,000,000 Hz
  • FM radio: 100,000,000 Hz
  • A microwave oven: 2,450,000,000 Hz
  • 5 GHz Wi-Fi: 5,000,000,000 Hz
  • Visible red light: 430,000,000,000,000 Hz
  • Visible violet light: 750,000,000,000,000 Hz

21 hertz in all frequency units

UnitValueScientific notation
Gigahertz (GHz) 2.1 × 10-82.1 × 10-8
Megahertz (MHz) 0.0000212.1 × 10-5
Kilohertz (kHz) 0.0212.1 × 10-2
Revolutions per minute (rpm) 1,2601.26 × 103
Beats per minute (bpm) 1,2601.26 × 103
Terahertz (THz) 2.1 × 10-112.1 × 10-11
Cycles per second (cps) 212.1 × 101
Revolutions per second (rps) 212.1 × 101
Cycles per minute (cpm) 1,2601.26 × 103
Per minute (min⁻¹) 1,2601.26 × 103
Per second (s⁻¹) 212.1 × 101
Millihertz (mHz) 21,0002.1 × 104
Per day (d⁻¹) 1,814,4001.8144 × 106
Per hour (h⁻¹) 75,6007.56 × 104
Petahertz (PHz) 2.1 × 10-142.1 × 10-14
Per week (wk⁻¹) 12,700,8001.27008 × 107
Per year (a⁻¹) 662,695,9926.62696 × 108
Exahertz (EHz) 2.1 × 10-172.1 × 10-17
Cycles per day (cpd) 1,814,4001.8144 × 106
Cycles per hour (cph) 75,6007.56 × 104
Microhertz (µHz) 21,000,0002.1 × 107
Planck frequencies (ωP) 1.1321621 × 10-421.13216 × 10-42
Fresnels (fresnel) 2.1 × 10-112.1 × 10-11

Other amounts of hertz

About the hertz

The hertz is the SI unit of frequency, one cycle per second. Read more about hertz.