Wavelength Calculator
Find wavelength and period from wave speed and frequency.
Sound ≈ 340 m/s, light ≈ 3×10⁸ m/s.
Results update as you type.
How it works
A wavelength is the physical distance between two matching points on a wave — crest to crest, or trough to trough — and this wavelength calculator finds it from the wave speed and the frequency you enter. It also reports the period, the time each full cycle takes. Every wave, whether sound rippling through air, light crossing space, or a ripple on water, obeys the same relationship: the faster it travels or the fewer cycles it completes each second, the longer each wave stretches out. Knowing wavelength matters across physics and engineering. Radio engineers size antennas to a fraction of a signal's wavelength, musicians and acousticians link pitch to the length of vibrating columns, and optical designers match lenses to the colours of light they must bend. Because the three quantities are locked together, fixing any two determines the wavelength, so the tool removes the division and unit juggling that trip people up. The relationship holds because speed equals wavelength times frequency, a direct consequence of a wave advancing one full wavelength during each cycle. Students checking homework, ham-radio operators tuning gear, and researchers working with sound or light all reach for a wavelength calculator to move from a measured speed and frequency to an exact answer.
wavelength = wave speed ÷ frequency
Wavelength equals wave speed divided by frequency because a wave advances exactly one wavelength during each complete cycle, so fitting more cycles into every second at the same speed packs the waves closer together. Frequency and wavelength are therefore inversely related for a fixed speed. The period, the time for one cycle, is simply one divided by frequency, since frequency counts how many cycles occur every second.
Source:Standard physics (wave equation)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter wave speed and frequency.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Wavelength updates instantly as you type — no button to press.
Frequently asked questions
What units should I use for wave speed and frequency?
Enter wave speed in metres per second and frequency in hertz, which counts cycles per second, and the wavelength comes out in metres. The period is returned in seconds. If your frequency is given in kilohertz or megahertz, multiply by one thousand or one million first, because keeping every input in base SI units guarantees the wavelength and period both come out correctly without extra scaling.
How are wavelength and frequency related?
For a wave travelling at a fixed speed, wavelength and frequency are inversely proportional: as one rises, the other falls. Double the frequency and each wave becomes half as long, because the same speed now has to fit twice as many cycles into every second. This trade-off explains why high-pitched sounds and high-frequency radio signals have short wavelengths while low tones stretch out far longer.
What is the period of a wave?
The period is the time it takes a wave to complete one full cycle, measured in seconds, and it is simply the reciprocal of frequency. A wave at two hertz repeats twice each second, so its period is half a second. Period and wavelength describe the same wave from different angles: one in time, the other in space, and both fall out of the frequency you enter.
Does this work for both sound and light?
Yes. The wave equation applies to every kind of wave, so you only need the correct speed for your medium. Sound travels at roughly 340 metres per second in air, while light and other electromagnetic waves move at about 300 million metres per second in a vacuum. Enter the appropriate speed for your situation and the calculator returns the matching wavelength and period for sound, light, or water waves.
Why does a speed of 340 and frequency of 170 give 2 metres?
Dividing the wave speed by the frequency gives the wavelength, so 340 metres per second divided by 170 hertz equals exactly 2 metres. This is a typical sound-wave example, since 340 metres per second is close to the speed of sound in air. The period works out as one divided by 170, roughly 0.0059 seconds, the time each cycle of that wave takes to pass.