Free Space Loss (Wi Fi) Calculator

Work out free space loss (wi fi) instantly with clear inputs, formula shown and shareable results.

About Free Space Loss (Wi Fi) Calculator

Free space path loss is 20log10(distance in km) + 20log10(frequency in MHz) + 32.45 dB, so loss rises 6 dB every time distance doubles and about 7.4 dB moving from 2.4 to 5 GHz. That frequency penalty is why 5 and 6 GHz cells are inherently smaller than 2.4 GHz ones at the same power.

Formula

Free space path loss

FSPL(dB) = 20 log10(d_km) + 20 log10(f_MHz) + 32.45; received = EIRP - FSPL - obstruction loss

Worked example

With the default values below, Free Space Loss (Wi Fi) Calculator returns Free space path loss of 87.26. Change any input above and every figure here is recalculated in your browser.

Inputs used

Distanceminimum 0.1 m: 100 m
Frequency bandone of 2.4 GHz, 5 GHz, 6 GHz: 5 GHz
Additional obstruction lossaccepts 0–100 dB: 10 dB
Effective radiated poweraccepts -10–40 dBm: 23 dBm

Results

Free space path loss: 87.26 dB
Total path loss with obstruction: 97.26 dB
Received signal level: -74.26 dBm
Usability at this level: Adequate for data

Step by step

1Values used
2Free space path loss
3Free space path loss= 87.26 dB
4Total path loss with obstruction= 97.26 dB
5Received signal level= -74.26 dBm
6Usability at this level= Adequate for data

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 or fees or charges 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

Why is the 6 GHz band worse for range?

Higher frequency means higher free-space loss and worse wall penetration. The trade is enormous spectrum with no legacy interference.

What obstruction losses are typical?

A plasterboard wall costs around 3 dB, a brick wall 6 to 10, concrete 10 to 20, and a foil-backed insulated wall or lift shaft can exceed 30 dB.