Frequency to Wavelength Conversion
Convert frequency and wavelength with velocity factor
Required Parameters
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Quick Answer
Wavelength (λ) = Velocity / Frequency. In a vacuum, velocity is the speed of light (c). In a cable or PCB, waves travel slower, requiring a Velocity Factor (VF) between 0.5 and 0.9.
Frequency to Wavelength Calculator
Convert between frequency and wavelength for electromagnetic waves. Essential for antenna design, RF engineering, and optics.
Formula
wavelength = c / f
Where c = speed of light (299,792,458 m/s) and f = frequency in Hz.
Common References
- 2.4 GHz WiFi = 12.5 cm wavelength
- 5 GHz WiFi = 6.0 cm wavelength
- 900 MHz cellular = 33.3 cm wavelength
- FM radio (100 MHz) = 3.0 m wavelength
- Visible light (600 THz) = 500 nm wavelength
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Design Notes
Never assume signals travel at the speed of light over a PCB or through a coaxial cable. For example, standard FR4 PCB material has a VF of roughly 0.45 to 0.55 depending on the trace geometry. This means a 1 GHz signal, which has a 30 cm wavelength in air, will only have a ~15 cm wavelength on your PCB. If you are designing quarter-wave matching stubs or length-matching high speed lines, using the correct velocity factor is critical.
Common Mistakes
- 1
Using c (300,000 km/s) for calculations inside coax cables. RG-58 coax typically has a VF of 0.66, meaning the wave is 34% slower.
- 2
Confusing Hz with MHz/GHz resulting in calculation errors off by millions. Always use base SI units or keep track of the scientific notation.
- 3
Ignoring the effect of dielectric loading. Exposing a trace to air vs encapsulating it in conformal coating changes the local velocity factor.
Engineering Handbox
1. Convert Frequency: 2.4 GHz = 2,400,000,000 Hz 2. Base Wavelength (Air): λ = c / f = 299,792,458 / 2.4e9 = 12.49 cm 3. Apply Velocity Factor: 12.49 cm × 0.66 = 8.24 cm
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