Link Budget Calculator

Work out link budget instantly with clear inputs, formula shown and shareable results.

About Link Budget Calculator

A link budget adds gains and subtracts losses in decibels: received power equals transmit power plus antenna gains minus path and cable loss. Subtracting receiver sensitivity gives the fade margin, and 10-20 dB is normally required to ride out rain, multipath and seasonal foliage.

Formula

Link budget

Prx = Ptx + Gtx + Grx - path loss - cable loss; margin = Prx - sensitivity

Worked example

With the default values below, Link Budget Calculator returns Link margin of 22.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Transmit power: 20 dBm
Total path loss: 114 dB
Combined antenna gain: 24 dBi
Receiver sensitivity: -92 dBm

Results

Link margin: 22.00 dB
Received signal power: -70.00 dBm
Effective isotropic radiated power: 32.00 dBm
Link assessment: Healthy margin

Step by step

1Values used
2Link budget
3Link margin= 22.00 dB
4Received signal power= -70.00 dBm
5Effective isotropic radiated power= 32.00 dBm
6Link assessment= Healthy margin

Assumptions and limits

The result is derived only from the 4 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

How much margin is enough?

10 dB for a short indoor link, 15-20 dB for an outdoor link, and more at frequencies above 10 GHz where rain fade is severe.

Why is sensitivity negative?

It is a power referenced to 1 mW, and receivers work with picowatts, so the dBm figure is a large negative number.