Frequency / Wavelength Calculator

Albert Michelson's 1879-1883 measurements of the speed of light at Case Western Reserve, accurate to 300 km/s, set the stage for the relationship λ = c/f to become foundational to radio engineering. Heinrich Hertz's 1887-1888 spark-gap experiments produced wavelengths of ~66 cm — the first deliberate generation of electromagnetic waves at what we now call 454 MHz — and confirmed Maxwell's prediction that light is electromagnetic radiation.

In 1983 the SI redefined the meter as "the length of the path traveled by light in vacuum during a time interval of 1/299792458 of a second" — fixing c to exactly 299,792,458 m/s by definition. Before this, the meter was the standard and c was measured; now c is the standard and the meter derives from it. This is why wavelength calculations use c with no uncertainty.

The velocity factor concept matters for transmission lines and antennas: in a dielectric (coax foam, FR4, Teflon), the wave propagates at v = c/√(ε_r) — typically 0.66c for RG-58 coax, 0.82c for RG-62 twin-lead, 0.5c for microstrip on FR4. Antenna designs use v-factor adjusted wavelengths when computing helical or loaded-section dimensions. For free-space antennas, VF = 1.

Enter a frequency (with optional units like MHz, GHz) and an optional velocity factor (default 1 for free-space radiation; use 0.66 for RG-58 coax, 0.83 for foam-dielectric coax, 0.5 for FR4 microstrip). The tool returns wavelength λ = c·VF/f, the half-wave (λ/2) dipole length, quarter-wave (λ/4) monopole length above a ground plane, and period T = 1/f.

Practical uses: antenna sizing (quarter-wave whip for 2.4 GHz WiFi = 31.2 mm in free air), PCB trace length vs wavelength (traces > λ/20 need transmission-line design), and cable matching (stubs are λ/4 long). For resonant antennas, add ~5% length compensation for end effects, or use NEC/MMANA simulation. Everything runs client-side; no values leave your browser.