How do I convert frequency to wavelength?

Use λ = v / f, where v is the wave speed in the medium and f is the frequency. For electromagnetic waves in vacuum, v = c = 299 792 458 m/s. Example: at 2.4 GHz (WiFi), λ = 299 792 458 / 2.4×10⁹ ≈ 0.125 m = 12.5 cm.

What's the difference between electromagnetic and acoustic waves?

Electromagnetic waves (radio, microwave, light) travel through vacuum at c ≈ 3×10⁸ m/s. Acoustic waves (sound) need a material medium and travel ~343 m/s in air or ~1480 m/s in fresh water — about a million times slower. Using the wrong medium for a wave type will give a wavelength that's off by ~10⁶.

How is the period of a signal calculated?

Period T is the time for one full cycle: T = 1 / f. A 1 kHz tone has a period of 1 ms; a 100 MHz FM radio signal has a period of 10 ns.

Why is the speed of light in vacuum exact?

Since the 1983 redefinition of the metre, c is fixed by definition at exactly 299 792 458 m/s (CODATA). The metre is defined as the distance light travels in 1/299 792 458 second — making c a defined constant, not a measured one.

Signal Frequency & Wavelength Calculator

Free wavelength-to-frequency calculator. Convert any value between frequency (Hz / kHz / MHz / GHz / THz), wavelength (km / m / cm / mm / µm) and period (seconds). Choose vacuum for electromagnetic waves (radio, WiFi, light) or air/water for sound, with NIST-grade physical constants.

Convert between frequency, wavelength and period for electromagnetic or acoustic waves.

v = f \cdot λ, T = \frac{1}{f}, λ = \frac{v}{f}

Formula

v = f \cdot λ, T = \frac{1}{f}, λ = \frac{v}{f}

Sources & References

CODATA Value: speed of light in vacuum (c = 299 792 458 m/s, exact)National Institute of Standards and Technology (NIST)
ITU-R Recommendation V.431 — Nomenclature of the frequency and wavelength bands used in telecommunicationsInternational Telecommunication Union (ITU)
Speed of sound — reference values for air and waterThe Engineering ToolBox

Disclaimer

Wavelength/frequency relations assume a non-dispersive, lossless medium. The 'vacuum' medium uses the exact CODATA value c = 299 792 458 m/s and applies to electromagnetic waves (radio, light). 'Air' (343 m/s at 20 °C) and 'water' (1480 m/s at 20 °C) use the speed of sound and apply only to acoustic (mechanical) waves. Real-world propagation depends on temperature, humidity, salinity, refractive index and frequency.

Last reviewed: 2026-05-27 by Numio editorial team.

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