Enter either a wavelength or a frequency — the other is solved from λ · f = v. Defaults to the speed of light for EM waves (radio, microwave, light, X-ray); switch to sound mode for acoustic wavelengths in air. Also shows photon energy (eV) and a half / quarter-wave dipole length for RF antenna design.
Presets
Inputs
m/s
c = 299 792 458 m/s (vacuum)
Results
Frequency
—
Wavelength
—
Period (T = 1/f)
—
Wavenumber (k = 2π/λ)
—
Photon energy (E = h·f)
—
Spectrum band
—
Half-wave / Quarter-wave (RF antenna)
—
Where on the EM spectrum?
3 Hz30 kHz30 MHz30 GHz30 THzvisibleUVX-rayγ-ray
Band
Frequency
Wavelength
Typical uses
Formulas
Wave equation: λ · f = v (v = c ≈ 3×10⁸ m/s for EM in vacuum)
Period: T = 1 / f
Wavenumber: k = 2π / λ (rad / m)
Photon energy: E = h · f = h · c / λ, h = 6.62607015×10⁻³⁴ J·s, 1 eV = 1.602176634×10⁻¹⁹ J
Half-wave dipole: L ≈ 0.95 · λ / 2 (velocity factor 0.95 for wire)