Wavelength Calculator
This wavelength calculator finds the wavelength of a wave from its frequency and speed, using λ = v / f. Enter the frequency and the wave speed and the wavelength calculator returns the wavelength in metres, centimetres, and millimetres. It works as a frequency to wavelength calculator for light, radio, and sound.
Results
The Wavelength Calculator is part of our Energy collection. Browse more energy to size, convert, and check your work alongside this tool.
What the wavelength calculator shows
A wave repeats over a distance called its wavelength, set by how fast it travels and how often it cycles. This wavelength calculator divides the wave speed by the frequency to give the wavelength. As a frequency to wavelength calculator it works for any wave once you set the right speed: the speed of light for radio and light, or the speed of sound for audio.
How the wavelength calculator uses frequency and speed
The wavelength calculator applies the wave relation:
λ is the wavelength, v is the wave speed, and f is the frequency. A higher frequency means a shorter wavelength at the same speed, which is why FM radio waves are metres long while visible light is under a millionth of a metre. The wavelength formula calculator rearranges to f = v ÷ λ for the reverse, so wavelength to frequency conversion is the same relation read the other way.
Frequency to wavelength calculator example
A 100 MHz FM radio signal travelling at the speed of light. The frequency to wavelength calculator gives:
So the wavelength is about 3 metres, or 300 cm. Change the frequency and the wavelength calculator updates every unit at once.
How to use the wavelength calculator
Enter the frequency in hertz and the wave speed in metres per second, then the wavelength calculator returns the wavelength in metres, centimetres, and millimetres. Use about 299,792,458 m/s for light and radio, or about 343 m/s for sound in air. As a wavelength and frequency calculator, the same relation runs the other way: divide the speed by a known wavelength to get the frequency.
Reading the wavelength calculator result
The wavelength is the distance between one wave crest and the next. Set the wave speed to match the medium: use the speed of light for radio, microwave, and visible light, and the speed of sound for audio and ultrasound. A quarter wavelength or half wavelength, common in antenna design, is simply the result divided by four or two. Because wavelength and frequency are tied by the fixed speed, raising one always lowers the other.
When to use the wavelength and frequency calculator
- Sizing an antenna with the wavelength and frequency calculator
- Converting a radio frequency to wavelength
- Finding a sound wavelength calculator result for audio
- Calculating frequency from wavelength for a known length
Common wavelength calculator mistakes
- Wrong wave speed. Use the speed of light for radio and light, and the speed of sound for audio.
- Mixing units. Enter the frequency in hertz; a megahertz is a million hertz.
- Forgetting the medium. The speed of sound changes with temperature and medium, which shifts the wavelength.
Tips for wavelength
- Match the wave speed to the medium, light or sound.
- Divide by four for a quarter wavelength antenna.
- Raising the frequency always shortens the wavelength.
Calculating frequency from wavelength
Calculating frequency from wavelength is the same wave relation turned around: f = v ÷ λ. If you know the length of a wave and how fast it travels, the frequency follows, which is how you find the frequency a given antenna length is tuned to. The fixed part is the speed: for radio and light it is the speed of light, so a longer wavelength always means a lower frequency, and finding wavelength given a frequency uses the same constant. This is why the radio spectrum is described both ways, by frequency in megahertz and by wavelength in metres. A frequency to wavelength converter and a wavelength to frequency converter are the same tool, since one number determines the other once the speed is set.
Sound wavelength calculator and audio wavelength calculator
A sound wavelength calculator and an audio wavelength calculator use the speed of sound, about 343 m/s in air at room temperature, not the speed of light. That is why sound wavelengths are so much longer for a given frequency: a 100 Hz bass tone is about 3.4 m long, while a 10 kHz treble tone is about 34 mm. Antenna and acoustic work often needs a fraction of a wavelength, so a quarter wavelength calculator or half wavelength calculator divides the result by four or two. The speed also shifts with the medium and temperature, so set the wave speed to match your case. For the general speed, distance, and time behind wave travel, the speed distance time calculator covers the basics.
Wavelength to frequency conversion chart
Wavelength at the speed of light by frequency, a quick wavelength to frequency conversion reference:
| Frequency | Wavelength | Band |
|---|---|---|
| 100 MHz | 3.00 m | FM radio |
| 433 MHz | 0.69 m | UHF remote |
| 2.4 GHz | 0.125 m | Wi-Fi |
| 5 GHz | 0.060 m | Wi-Fi |
Wavelength Calculator FAQ
What is the wavelength formula?
The wavelength formula is lambda = v divided by f, wave speed divided by frequency. The wavelength calculator applies it and shows the result in metres, centimetres, and millimetres.
How do I do a wavelength to frequency conversion?
Divide the wave speed by the wavelength: f = v divided by lambda. It is the same relation as frequency to wavelength, read the other way.
What speed should I use?
About 299,792,458 m/s for light and radio, and about 343 m/s for sound in air. A sound wavelength calculator uses the speed of sound, not the speed of light.
What is a quarter wavelength?
It is the wavelength divided by four, used in antenna design. A quarter wavelength calculator just takes the wavelength result and divides by four.