📡 Free Space Path Loss Calculator
Calculate the free space path loss of a radio signal between a transmitter and receiver, based on frequency and distance.
What free space path loss is
Free space path loss (FSPL) describes how much a radio signal weakens as it travels through open space between a transmitter and receiver, assuming no obstacles, reflections, or atmospheric absorption — an idealized baseline used in wireless link budgets.
The formula
FSPL (dB) = 20log₁₀(d) + 20log₁₀(f) + 32.44, where d is the distance in kilometers and f is the frequency in megahertz. This is the standard simplified Friis free-space path loss formula widely used in RF and wireless network link budget calculations.
Real-world signal loss also includes atmospheric absorption, terrain, obstacles, and multipath effects not captured by this idealized formula.