Wireless Link Budget Calculator

Build a complete point-to-point RF link budget: transmit power, antenna gain, cable loss, path loss and receiver sensitivity, with the fade margin that decides availability.

Calculator WiFi & Wireless Runs in your browser
From the datasheet, for the modulation you need.
Obstruction, misalignment, radome, rain.
Try:

Result

Received signal level
-64.25 dBm
Fade margin
13.75 dB
EIRP at antenna A
43 dBm
Free space path loss
127.25 dB
Expected availability
usable, expect weather outages
Total system gain
46 dB

Budget breakdown

ElementdB / dBm
TX power+20
Cable/connector loss A-1
Antenna A gain+24
Free space path loss (10 km, 5500 MHz)-127.2
Additional losses-3
Antenna B gain+24
Cable/connector loss B-1
Received signal level-64.2 dBm
Receiver sensitivity-78 dBm
Fade margin13.8 dB
Moderate margin
Between 10 and 20 dB of margin gives a working link that will drop to lower modulation rates in rain. Acceptable for best-effort, not for a backhaul carrying customers.

About Wireless Link Budget Calculator

A link budget is simple bookkeeping in decibels: everything that adds power, everything that removes it, and whether what arrives is comfortably above what the receiver needs. The interesting number is not signal level but fade margin - the headroom that keeps the link up when the weather changes.

Availability targets and rain

Fade margin buys availability. Roughly 20 dB corresponds to about 99.9% on a temperate 5 GHz hop, and 25 to 30 dB to 99.99% — the difference between nine hours and 53 minutes of annual outage. Rain attenuation is negligible below about 6 GHz, noticeable at 11 GHz and dominant at 24 GHz and above, where ITU-R P.530 rain-region statistics rather than a flat margin should drive the design.

Sensitivity is per modulation

Datasheets quote sensitivity per MCS rate. The headline figure is usually the most robust, slowest modulation - a link that "works" at that level may deliver a fraction of the throughput you sold. Budget against the sensitivity of the modulation you actually need, which is typically 15-25 dB less sensitive than the headline.

Common use cases

  • Designing a point-to-point backhaul before buying radios.
  • Diagnosing a link that works in summer and fails in rain.
  • Deciding whether more antenna gain or a shorter hop is the cheaper fix.

Edge cases and gotchas

  • EIRP is regulated: check that TX power minus cable loss plus antenna gain stays within your local limit.
  • Cable loss at 5 GHz is severe - keep coax runs short or mount the radio at the antenna.

Frequently asked questions

How much fade margin is enough?
20 dB is the usual target for a link expected to stay up, 25-30 dB for carrier-grade availability in rain-prone regions. Below 10 dB the link is a fair-weather link.
Why is my real RSSI worse than calculated?
Alignment error, Fresnel obstruction, connector water ingress and interference all cost dB that a budget cannot see. A 3-6 dB gap between calculation and reality is normal; more than 10 dB means something is wrong.