〰️ Wavelength Calculator (v = fλ)
Relate wave speed, frequency and wavelength (v = fλ), enter any two to get the third.
Wavelength λ
2 m
Wave equation: v = f·λ (speed = frequency × wavelength). For light, v = c = 3×10⁸ m/s; period T = 1/f. 🔒 Computed in your browser.
How the wavelength calculator (v = fλ) works
For any wave, speed = frequency × wavelength: v = fλ. Enter any two of the three and the tool solves for the last. For light in a vacuum, v = c = 3×10⁸ m/s; for sound in air, about 340 m/s. Period T = 1/f. The same relation gives any one quantity from the other two, divide speed by frequency for the wavelength, or divide speed by wavelength for the frequency.
One equation for all waves. Higher frequency means shorter wavelength at a fixed speed, the reason blue light has a shorter wavelength than red.
Frequently asked questions
How do I calculate wavelength?
Divide the wave speed by the frequency: λ = v/f. A 170 Hz sound in air (340 m/s) has λ = 2 m. Enter speed and frequency to compute it.
What is the wave equation?
v = fλ: wave speed equals frequency times wavelength. It applies to sound, light, water waves and all other waves.
What speed do I use for light?
The speed of light, c = 299,792,458 m/s (about 3×10⁸ m/s) in a vacuum. In a medium it’s slower by the refractive index.
How are frequency and wavelength related?
Inversely, at fixed speed: higher frequency ⇒ shorter wavelength. Doubling the frequency halves the wavelength.
What is the period of a wave?
The time for one cycle, T = 1/f. A 170 Hz wave has a period of about 5.9 ms.
Worked example: an FM radio wave
A 100 MHz FM signal travels at the speed of light: λ = c/f = 3×10⁸ / 100×10⁶ = 3 m. Radio waves have much longer wavelengths than visible light because their frequency is far lower.
Why is the wave speed sometimes treated as fixed?
For a given medium the speed is roughly constant, light in a vacuum always travels at c, and sound in air near 343 m/s, so changing the frequency changes the wavelength inversely. In a different medium the speed, and hence the wavelength, shifts.
What is the wavelength of audible sound?
Human hearing spans roughly 20 Hz to 20 kHz. In air at 343 m/s that is wavelengths from about 17 m (deep bass) down to about 1.7 cm (high treble), all from λ = v/f.
How does the wavelength change in a different medium?
When a wave enters a new medium its frequency stays the same but its speed changes, so the wavelength changes in proportion (λ = v/f). Light slows and its wavelength shortens on entering glass or water.