Power Calculators

〰️ Frequency Calculator (Hz from Wavelength, Period or ω)

Hertz from any of the usual starting points — with the related wave quantities.

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Formula at a glance

Frequency Calculator: From wavelength — f = v / λ. Example: Green light, 500 nm → Frequency: 599.585 THz
How the Frequency Calculator works: From wavelength — f = v / λ

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📘 About the Frequency Calculator

Frequency is how many cycles happen per second, measured in hertz (Hz). It links to the period (the time for one cycle, T = 1/f), angular frequency (ω = 2πf) and wavelength through the wave equation v = fλ. Frequency sets the pitch of a sound, the colour of light and the channel of a radio.

Choose what you know — wavelength and speed, period, angular frequency or RPM. The calculator gives the frequency in convenient units, the period, ω, the wavelength for the chosen wave speed, the photon energy for light and which part of the spectrum it falls in.

🧮 Formula

From wavelength
f = v / λ
From period
f = 1 / T
From angular frequency
f = ω / 2π
Photon energy
E = hf

✏️ Worked examples

Green light, 500 nm

You enter
Find frequency fromWavelength and wave speed (f = v/λ)
Wavelength λ500
Wavelength unitnm
Wave speedLight / radio (299,792,458 m/s)
Other speed343 m/s
Period T0.02
Period unitseconds
Angular frequency ω314.16 rad/s
RPM3000
You get
Frequency599.585 THz
In hertz599584916000000 Hz
Period T = 1/f1.66782 × 10^-15 s
Angular frequency ω = 2πf3.7673 × 10^15 rad/s
Wavelength λ = v/f (v = 299792458 m/s)5 × 10^-7 m
Photon energy E = hf3.973 × 10^-19 J = 2.4797 eV
Formula usedf = v/λ
RangeVisible light

599.585 THz.

Mains AC, period 20 ms

You enter
Find frequency fromPeriod (f = 1/T)
Wavelength λ500
Wavelength unitnm
Wave speedLight / radio (299,792,458 m/s)
Other speed343 m/s
Period T20
Period unitmilliseconds
Angular frequency ω314.16 rad/s
RPM3000
You get
Frequency50 Hz
In hertz50 Hz
Period T = 1/f0.02 s
Angular frequency ω = 2πf314.159 rad/s
Wavelength λ = v/f (v = 299792458 m/s)5995849 m
Photon energy E = hf3.313 × 10^-32 J = 2.0678 × 10^-13 eV
Formula usedf = 1/T
RangeAudible sound range (20 Hz – 20 kHz)

50 Hz.

🧭 How to use this calculator

What you enter

  • Find frequency from
  • Wavelength λ
  • Wavelength unit
  • Wave speed
  • Other speed (m/s)
  • Period T
  • Period unit
  • Angular frequency ω (rad/s)
  • RPM

What you get

  • Frequency
  • In hertz
  • Period T = 1/f
  • Angular frequency ω = 2πf
  • Wavelength λ = v/f (v = 299792458 m/s)
  • Photon energy E = hf
  • Formula used
  • Range

❓ Frequently asked questions

What is the formula for frequency?

f = 1/T from the period, or f = v/λ from the wave speed and wavelength.

What is the frequency of visible light?

About 400–790 THz (wavelengths 750–380 nm).

How are frequency and wavelength related?

Inversely: for the same speed, doubling the frequency halves the wavelength.

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