Wavelength Calculator

How to use the Wavelength Calculator

1. 1Enter the frequency, its unit, and the kind of wave.
2. 2Pick the units or options from the menus if the wavelength tool offers them.
3. 3Read the wavelength in the large result box.
4. 4Look at the extra rows for related figures.
5. 5Press Copy result to keep the answer.

When you need the wavelength

Radio amateurs use it to cut antennas, since a half-wave dipole is half a wavelength long. Audio engineers use it to understand room acoustics, where a low note with a wavelength of several metres fits between walls in a particular way.

Photographers and scientists use it for light: the wavelength sets the colour. The calculator shows results in the best unit, such as millimetres for microwaves and metres for FM radio.

How the wavelength is worked out

Wavelength = wave speed ÷ frequency. The period is 1 ÷ frequency. A 100 MHz FM radio signal travels at 299,792,458 m/s, so its wavelength is 2.998 m. A 440 Hz musical note in air at 20 °C has a wavelength of 343 ÷ 440 = 0.78 m. Wi-Fi at 2.4 GHz has a wavelength of 12.5 cm.

Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.

• Light, radio and sound speeds
• Custom speed
• Half and quarter wavelength shown

Mistakes to avoid with wavelength

Wave speed depends on the medium. Light slows down in glass, and sound speed changes with temperature. Choose the option that matches your case, or enter the speed yourself. Real antennas are usually cut a few percent shorter than the free-space figure.

On phone and computer

On a phone, type into the boxes one after another and read the wavelength underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the wavelength move. The wavelength calculator works the same on both. Use Frequency Converter to enter the frequency in the right unit, Unit Converter for lengths, Decibel Calculator for signal level, and dBm Converter for radio power.

Features

• Higher frequency, shorter wavelength
• Speed depends on the medium
• Cut antennas a little short
• Clear messages when the wavelength inputs make no sense
• Copy the result with one tap
• Private: nothing is uploaded

Frequently asked questions