Free-Space Path Loss Calculator
Calculate the free-space path loss in dB between two antennas from distance and frequency, plus the wavelength.
Free-space path loss–
Wavelength λ–
Distance in wavelengths (d / λ)–
Free-space path loss
As a radio wave spreads out from an antenna, its power is diluted over an ever-larger sphere. Free-space path loss (FSPL) is that geometric spreading loss between two antennas with a clear line of sight and no obstacles.
FSPL(dB) = 20·log₁₀(d) + 20·log₁₀(f) − 147.55
with distance d in metres and frequency f in hertz. Loss rises by 6 dB each time the distance doubles, and by 6 dB each time the frequency doubles — so higher bands need more link budget for the same range.
Related
Feed this figure into theRF link budget calculator to find the received power and link margin, or size an antenna with thewavelength calculator.