Wavelength to Frequency Calculator — f = v / λ
Enter a wavelength in any unit (nanometres to kilometres) and choose electromagnetic or a custom wave speed to get frequency in Hz, kHz, MHz, GHz, or THz — plus period, angular frequency, and wavenumber.
Wavelength unit
Wave type
Frequency unit
Number of wave cycles per second at this wavelength
- 1
Wavelength in metres
550 × 1e-9 = 5.500e-7 m - 2
Frequency f = v ÷ λ
2.998e+8 ÷ 5.500e-7 = 5.451e+14 Hz - 3
Convert to THz
5.451e+14 × 1e-12 = 545.0772
How does this calculator work?
f = v/λ converts wavelength to frequency. For electromagnetic waves in vacuum v = c = 2.998×10⁸ m/s. Enter any wavelength from pm to km and get frequency in your choice of Hz, kHz, MHz, GHz, or THz, plus period and angular wavenumber.
Formula
How this is calculated
Frequency and wavelength are inversely related through a wave’s speed: f = v / λ. For electromagnetic waves travelling through vacuum the speed is the constant c = 2.99792458 × 10⁸ m/s, so a 550 nm green photon oscillates at about 545 THz. For other wave types — sound in air, ultrasound, seismic waves — enter the relevant wave speed instead.
The calculator converts your wavelength input to metres, then divides the wave speed by it to get frequency in Hz. It then scales that to your chosen output unit (Hz through THz) for readability. Period T = 1/f and angular frequency ω = 2πf are derived directly; angular wavenumber k = 2π/λ is a spatial equivalent of ω used in wave equations and quantum mechanics.
For EM waves, the formula gives the frequency in vacuum (or essentially in air). Inside a medium with refractive index n, the wave slows to c/n and the wavelength shortens to λ/n, but frequency remains the same because frequency is set by the source. If you know the in-medium wavelength, the Custom speed option lets you enter the actual speed in that medium.
Frequently asked questions
Use f (THz) ≈ 299792.458 / λ (nm). For example 550 nm gives 299792.458 / 550 ≈ 545 THz. This is a direct application of f = c/λ with c in nm/ps.
Not in a non-dispersive medium. The speed is a property of the medium. Changing wavelength changes frequency proportionally so their product stays equal to v. In a dispersive medium (e.g. glass for light) speed varies slightly with wavelength.
2.4 GHz corresponds to λ = c/f = 2.998×10⁸ / 2.4×10⁹ ≈ 0.125 m (12.5 cm). The 5 GHz band is about 6 cm. These are microwave wavelengths, far longer than visible light.
Also known as
TG we-Calculate Editorial Team. (2026). Wavelength to Frequency Calculator — f = v / λ [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/wavelength-to-frequency-calculator
TG we-Calculate Editorial Team. "Wavelength to Frequency Calculator — f = v / λ." TG we-Calculate. 2026. https://we-calculate.com/calculator/wavelength-to-frequency-calculator.
TG we-Calculate Editorial Team, "Wavelength to Frequency Calculator — f = v / λ," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/wavelength-to-frequency-calculator
@misc{wecalculate_wavelength_to_frequency_calculator, title = {Wavelength to Frequency Calculator — f = v / λ}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/wavelength-to-frequency-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?