Wireless Link Budget Calculator
Calculate received signal power from transmit power, antenna gains, path loss, and cable loss.
Inputs
Minimum signal the receiver needs for a usable link
Received Power
-62.00dBm
Link Margin
23.00dB
EIRP
23.00dBm
Step by step
Values used
Transmit Power = 20 dBm; Transmit Antenna Gain = 5 dBi; Receive Antenna Gain = 5 dBi; Path Loss = 90 dB; Cable/Connector Loss = 2 dB; Receiver Sensitivity = -85 dBm
Received power
received_power = Tx_power + Tx_gain + Rx_gain − path_loss − cable_loss
Link margin
margin = received_power − receiver_sensitivity
Received Power
= -62.00 dBm
Link Margin
= 23.00 dB
EIRP
= 23.00 dBm
How it works
A wireless link budget adds every gain and subtracts every loss along the signal path, in dB, to predict the power arriving at the receiver: received power = Tx power + Tx antenna gain + Rx antenna gain − path loss − cable/connector loss. The link margin (received power minus receiver sensitivity) indicates how much headroom the link has — a positive margin means the link should work, and a larger margin means more tolerance for fading, rain, or other unmodeled losses.
Formulas
Received power
received_power = Tx_power + Tx_gain + Rx_gain − path_loss − cable_loss
Link margin
margin = received_power − receiver_sensitivity
Frequently Asked Questions
What is EIRP and how does it relate to this budget?
EIRP (Effective Isotropic Radiated Power) is the transmit power as seen in the direction of maximum antenna gain, after accounting for cable loss: EIRP = Tx power + Tx antenna gain − cable loss. Many regulatory bodies cap EIRP rather than raw transmitter output power.
How much link margin is considered safe?
A margin of at least 10-20 dB is commonly recommended for outdoor point-to-point links to account for rain fade, seasonal foliage changes, and minor alignment drift; indoor short-range links can often tolerate a smaller margin since conditions are more stable.
Where does path loss come from in this formula?
Path loss is typically calculated separately (e.g. using free-space path loss or a terrain-aware propagation model) and entered here as a single dB value — see the Fresnel Zone or Microwave Link calculators for how to estimate it for a specific distance and frequency.
Why subtract cable loss separately from path loss?
Path loss models the loss of the wireless signal traveling through the air between antennas, while cable loss is the separate, physical loss in the feedlines and connectors between the radio and the antenna itself — both reduce the usable signal but come from different sources.