Wireless Link Budget
Calculate the complete link budget for a wireless link including gains and losses.
About Wireless Link Budget
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
Worked example
With the default values below, Wireless Link Budget returns Received Power of -62.00. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Transmit Power
- 20 dBm
- Transmit Antenna Gain
- 5 dBi
- Receive Antenna Gain
- 5 dBi
- Path Lossminimum 0 dB
- 90 dB
- Cable/Connector Lossminimum 0 dB
- 2 dB
- Receiver Sensitivity
- -85 dBm
Results
- Received Power
- -62.00 dBm
- Link Margin
- 23.00 dB
- EIRP
- 23.00 dBm
Step by step
- 1Values used
- 2Received power
- 3Link margin
- 4Received Power= -62.00 dBm
- 5Link Margin= 23.00 dB
- 6EIRP= 23.00 dBm
Assumptions and limits
- The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.