Work out WiFi range and coverage area from transmit power, band and building type using the ITU-R P.1238 indoor model, with a real shadow-fade margin.
α = 4.0 from ITU-R P.1238-13 §3.2 (through walls between rooms, coefficient about 40); σ = 5.01 dB from Table 2, Office NLoS.
Share of locations at the cell edge that must still meet your sensitivity target. 90% is the usual design point.
This environment already includes typical wall and obstruction loss, so walls are not counted again. Choose "Clear line of sight" to count walls one by one.
Coefficients for L = 10α·log₁₀(d) + β + 10γ·log₁₀(f). Rows with a fitted range come straight from Recommendation ITU-R P.1238-13, Table 2; the others take α from its §3.2 general conclusions for the 900-2000 MHz band, β and γ from its equation (2), and σ from the Table 2 row named under the selector. An em dash means the source states no fitted range. A result beyond a stated fitted distance is an extrapolation.
| Environment | α | β | σ (dB) | Fitted |
|---|---|---|---|---|
| Line of sight — count walls | 2 | 32 | 3.68 | — |
| Home or office, through walls | 4 | 32 | 5.01 | — |
| Open-plan office | 2.39 | 30.13 | 5.01 | 4-30 m |
| Warehouse or factory | 2.8 | 23.55 | 5.7 | 3-110 m |
| Long corridor | 1.8 | 32 | 7.58 | — |
Loss through one wall. Concrete and wood are the two figures ITU-R P.1238-13 states per wall; the rest are typical values in common use, taken at the pessimistic end.
| Material | 2.4 GHz | 5 GHz | 6 GHz | Source |
|---|---|---|---|---|
| Drywall / plasterboard | 3 dB | 4 dB | 5 dB | Typical |
| Wood | 4 dB | 7 dB | 8 dB | Standard |
| Glass | 3 dB | 4 dB | 5 dB | Typical |
| Concrete | 10 dB | 13 dB | 16 dB | Standard |
| Brick | 8 dB | 12 dB | 15 dB | Typical |
| Metal | 25 dB | 30 dB | 35 dB | Typical |
A propagation estimate, not a site survey. Real buildings vary; measure before committing to a design.
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WiFi range is set by a link budget: how much power leaves the access point, how much the walls and distance take away, and how weak a signal the client will still hold. This calculator runs that budget on the ITU-R P.1238 indoor propagation model, applies a real shadow-fade margin so the answer is a design range rather than a lucky median, and tells you when the result has run past the distance the model was measured over.
Indoor propagation is modelled empirically, not from first principles: measurements across many buildings are fitted to a distance exponent, an offset and a frequency exponent, plus a standard deviation describing how much any single spot varies from that fit. Recommendation ITU-R P.1238 publishes those coefficients by environment. The fitted curve gives the median path loss; the standard deviation is what turns a median into a design figure, because half of all locations are worse than the median by definition.
ITU-R P.1238 site-general model
Check whether the far bedroom sits inside the design range, and what signal level a device there would actually see.
Divide the floor area by the hexagonal cell each AP truly serves, rather than by the full circle, which overlapping cells never deliver.
Run the same room three times and see how much range each band costs you before committing to a dual or tri-band design.
Put a number on what two concrete walls cost, using the per-wall figures ITU-R P.1238 states.
A median range is met by only half the locations at the cell edge. This calculator subtracts a shadow-fade margin of z × σ, using the standard deviation published alongside the coefficients, so a 90% target really means 90% of edge locations.
ITU-R P.1238 is explicit that its distance coefficients already include an allowance for transmission through walls. Adding a per-wall figure on top of a through-wall environment counts the same loss twice, so the wall inputs appear only on the clear-line-of-sight model, which carries no such allowance.
Access points and phones are not the same antenna. A 6 dBi AP paired with a 0 dBi handset is the normal case, and entering one gain for both ends overstates the link budget by several dB.
Each coefficient set was fitted over a stated distance range — 4 to 30 m for the office model. When the computed range runs past that, the result says so instead of quietly reporting a number no measurement supports.
Vendor range figures are usually free-space, line-of-sight, median values with a generous sensitivity threshold. This calculator uses an indoor model fitted to real buildings and subtracts a fade margin, so it answers a different question: how far can you rely on the signal, not how far can it ever reach.
Measured path loss scatters around the fitted curve with a standard deviation σ of roughly 3.7 to 7.6 dB indoors. The fitted curve is the median, so half of all spots at that distance are worse. Reserving z × σ of extra budget — about 1.28σ for 90% — buys you the coverage probability you asked for, and that reserved budget is range you no longer get to spend.
ITU-R P.1238-13 states about 10 dB per concrete wall at 2.4 GHz and 13 dB at 5.2 GHz. Drywall, glass, brick and metal figures in the table below are typical values in common use rather than standardised ones, taken at the pessimistic end.
Around −67 dBm is the level normally specified for voice and video, −60 dBm and better is comfortable for everything, and below about −75 dBm links become slow and unstable. These are engineering conventions rather than a standard.
Each ITU coefficient set was fitted over a stated distance range. The office model was measured from 4 to 30 m. Feeding it a link budget that implies 150 m produces a number, but nothing in the underlying measurements supports it, so the calculator flags it as an upper bound rather than a prediction.
Rarely. The client has to answer, and a phone transmits at far less power than an access point, so raising AP power alone creates a cell where devices hear you and you cannot hear them. It also makes clients cling to a distant AP instead of roaming. Adding an access point almost always beats turning one up.