Wavelength Calculator

Worked example: FM radio at 100 MHz

The core formula is λ = v/f — wavelength equals wave velocity divided by frequency. Enter frequency = 100 with unit MHz, and leave velocity at its default (299,792,458 m/s, the speed of light in vacuum), with result unit set to meters:

frequency in Hz = 100 × 1,000,000 = 100,000,000 Hz
λ = v / f = 299,792,458 / 100,000,000 = 2.9979246 m

That's roughly 3 meters — consistent with commercial FM radio (88-108 MHz), where antenna elements are typically built around a quarter-wavelength (~75 cm) for practical size reasons. Compare that to a 2.4 GHz Wi-Fi signal: λ = 299,792,458 / 2,400,000,000 ≈ 0.1249 m, about 12.5 cm — showing why higher-frequency waves need much smaller antennas.

Switching the velocity preset changes the whole answer

The same 100 MHz frequency through a different medium gives a different wavelength, since v isn't fixed — it's the speed of the wave in whatever medium you specify. Selecting the "speed of sound in air" preset (343 m/s) instead of light-in-vacuum for that same 100 MHz frequency would give λ = 343/100,000,000 = 0.00000343 m, a wavelength about a million times shorter — because sound travels roughly a million times slower than light.

Reading small results in scientific notation

When the computed wavelength in your selected unit falls below 0.001, the tool switches to scientific notation (e.g., 3.43e-6) rather than printing a long string of leading zeros — this typically happens with high frequencies paired with slow wave speeds, like sound at MHz-range frequencies.

Unit conversion under the hood

Both frequency and velocity inputs are first normalized to base SI units (Hz and m/s) using the unit dropdown's multiplier before the division happens, then the meter-based result is divided again by your chosen output unit's conversion factor — so switching units never changes the underlying physics, only the display.