RF Link Budget Calculator
Free-space path loss, received power and link margin for a wireless link.
Input
ℹ FSPL = 20log(d_km) + 20log(f_MHz) + 32.45.
Results
Free-Space Path Loss—
Received Power—
Link Margin—
💡 Usage & Formula
Prx = Ptx + Gtx + Grx − FSPL − Lother; margin = Prx − sensitivity. A positive margin (typ. >10 dB) means the link closes.
When you need it: Estimating received power and link margin over a wireless path from transmit power, antenna gains and path loss — the go/no-go check for a radio range.
Worked example: Prx = Ptx + Gtx + Grx − FSPL = 10 + 2 + 2 − 90 = −76 dBm. If the receiver sensitivity is −95 dBm, the link margin is 19 dB.
Tips & gotchas:
- Aim for at least 10–20 dB of fade margin; free-space path loss is a best case that real environments never quite hit.
- Add clutter, multipath and rain/foliage losses on top of FSPL for a realistic budget.
- Cable, connector and mismatch losses at each end come straight off the margin.
- Doubling frequency adds 6 dB of path loss for the same distance — a real cost of going higher in band.
📖 References:Link budget (Wikipedia)