Frequency and Wavelength Converter

Convert between frequency and wavelength for light, radio, and other electromagnetic waves in any medium.

Frequency and Wavelength Converter tool

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Example

Input: 2.4 GHz (Wi-Fi band) in vacuum, frequency to wavelength

Result: Wavelength 12.4914 cm (period 416.6667 ps, microwave region)

Wavelength = c / f = 299,792,458 / 2,400,000,000 = 0.124914 m = 12.4914 cm.

Common Frequencies and Their Wavelengths

FrequencyUseWavelengthQuarter wave
1 MHzAM radio299.79 m74.95 m
27.185 MHzCB radio11.03 m2.76 m
100 MHzFM radio2.998 m74.95 cm
433.92 MHzRemote controls69.09 cm17.27 cm
915 MHzISM band (Americas)32.76 cm8.19 cm
2.4 GHzWi-Fi, Bluetooth12.49 cm3.12 cm
5 GHzWi-Fi6.00 cm1.50 cm
60 GHzShort-range wireless5.00 mm1.25 mm

In a vacuum, using c = 299,792,458 m/s.

  1. Choose the conversion mode - Frequency to Wavelength or Wavelength to Frequency.
  2. Select the propagation medium - vacuum, air, water, or glass - which sets the wave speed.
  3. Enter the frequency or wavelength value you want to convert in the Value field.
  4. Select the input unit (Hz, kHz, MHz, GHz, THz for frequency or km, m, cm, mm, micrometers, nm, pm for wavelength).
  5. View the converted result along with the period, photon energy, and electromagnetic spectrum region.
  6. For RF antennas, divide the resulting wavelength by 4 for a quarter-wave or by 2 for a half-wave element.

Converting Frequency to Wavelength

Wavelength equals wave speed divided by frequency. For radio and light in a vacuum, the speed is c = 299,792,458 m/s, so a 100 MHz FM signal has a wavelength of about 3 meters. A 2.4 GHz Wi-Fi signal has a wavelength of 12.49 cm.

A quick rule for radio is 300 divided by the frequency in MHz gives the wavelength in meters. The converter works in both directions. Pick Frequency to Wavelength or Wavelength to Frequency, enter a value, and choose units from Hz to THz or from km to pm. Each result also shows the period, the time for one full cycle. You also see the photon energy in electron volts and the part of the spectrum the wave falls in, from radio through microwave, infrared, visible light and ultraviolet to X-rays and gamma rays.

Waves slow down in materials, and so does the wavelength, while the frequency stays the same. The Medium menu lets you pick air, water (n = 1.333) or glass (n = 1.5). The refractive index n tells you how many times slower the wave travels there. Light at a given frequency has a wavelength in glass about two thirds of its vacuum value. Keep vacuum for antenna and radio work. Air differs by only 0.03%. For antennas, a quarter-wave element is the wavelength divided by 4. At 433 MHz that is about 17.3 cm before any trimming. For signal levels in the same projects, the Decibel Calculator converts watts to dBm.

Formula / How It Works

Wavelength = Speed / Frequency | In vacuum: lambda = c / f (c = 299,792,458 m/s) | In a medium: v = c / n | Period = 1 / f | Photon energy E = h x f

Sources

Frequently Asked Questions

Divide 300 by the frequency in MHz. That uses the speed of light, rounded to 300 million m/s. For 100 MHz the answer is 3 m, and for 27 MHz it is about 11 m. The converter uses the exact value, 299,792,458 m/s, so 100 MHz shows as 2.9979 m.
2.4 GHz has a wavelength of about 12.49 cm, and 5 GHz about 6.0 cm. A quarter-wave antenna is about 3.1 cm and 1.5 cm long. Shorter waves are absorbed more by walls, which is part of why 5 GHz Wi-Fi has less range than 2.4 GHz.
Visible light runs from about 380 nm (violet) to 750 nm (red), which is roughly 790 THz down to 400 THz. Enter a wavelength in nm with Wavelength to Frequency mode to get the exact value. For example, 550 nm green light is about 545 THz, with a photon energy of about 2.25 eV.
No. The frequency stays the same, and the speed and wavelength both drop by the refractive index. In glass with n = 1.5, light moves at about 200,000 km/s, so its wavelength is two thirds of the vacuum value. The converter shows this when you change the medium.

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