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Calcimator

Free Space Path Loss Calculator

Calculate free space path loss (FSPL) from distance and frequency. Includes received signal power estimation.

Inputs

MHz
km
dBm
dBi
dBi

Results

Free Space Path Loss

91.52 dB

Received Power

-61.52 dBm

Received Power0 W
Wavelength0.3331 m
How to Use This Calculator
  1. Enter the link frequency (MHz or GHz) and path distance.
  2. Enter transmit power and antenna gains for both ends of the link.
  3. Review free-space path loss (dB) and estimated received power in dBm and watts.
  4. Use received power vs. your receiver sensitivity to determine link margin.

How the result changes with Frequency

FrequencyFree Space Path LossReceived Power
10,001112.44 dB-82.44 dBm
35,001123.32 dB-93.32 dBm
65,000128.7 dB-98.7 dBm
90,000131.52 dB-101.52 dBm

What each input means

Frequency
Signal frequency in megahertz
Distance
Distance between transmitter and receiver in kilometers
Transmit Power
Transmitter output power in dBm (30 dBm = 1 watt)
Transmit Antenna Gain
Transmit antenna gain in dBi (0 = isotropic)
Receive Antenna Gain
Receive antenna gain in dBi (0 = isotropic)

How this is calculated

Formula

FSPL (dB) = 20·log₁₀(d) + 20·log₁₀(f) + 32.44

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Frequency = 900, Distance = 1, Transmit Power = 30, Transmit Antenna Gain = 0 = 5 input(s) provided
  2. Calculate Free Space Path Loss
    Free Space Path Loss
    91.52 = 91.52
  3. Calculate Received Power
    Received Power
    -61.52 = -61.52
  4. Calculate Received Power
    Received Power = Number(receivedPowerWatts.toExponential(3))
    7.039e-10 = 7.039e-10
  5. Calculate Wavelength
    Wavelength
    0.3331 = 0.3331

Engine last updated . Checked against 4 independently-derived tests — how we verify calculators.

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