ONE FORMULA, ONE ANSWER
Free-Space Path Loss Calculator
Calculate isotropic-reference path loss caused by geometric spreading in far-field free-space propagation. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Free-space path loss L_FS
Enter values and select Calculate.
L_FS = 20 log₁₀(4πdf/c)
Assumptions
Required: an unobstructed free-space path and both antennas operating in each other’s far field. The tool checks only d ≥ λ; the far-field distance imposed by actual antenna dimensions requires a separate check. Excluded: antenna gains, feeder losses, polarization mismatch, ground reflection, diffraction and atmospheric absorption. This is the isotropic-reference spreading loss rather than the full link loss.
Displayed values are floating-point approximations. Design safety factors and unprovided error contributions are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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