Coverage Heatmap Estimator
Estimate indoor cell radius, cell area and AP count from EIRP, target RSSI, wall losses and a path-loss exponent.
About Coverage Heatmap Estimator
The one-slope indoor model anchors path loss at a one-metre reference and then grows it by 10·N decibels per decade of distance. Solving it for distance at the point where received power equals the target RSSI gives the cell radius; multiplying the circle area by 0.65 accounts for overlap and non-circular real-world cells. Predictive designs live or die on the path-loss exponent and wall losses — assume free space indoors and you will deploy half the APs you need, then re-survey after go-live.
Formula
Coverage Heatmap
PL(d) = 20·log10(f_MHz) − 27.56 + 10·N·log10(d_m), inverted for d at a link budget of EIRP − target RSSI − wall losses − fade margin.
- N
- Path-loss exponent: 2 in free space, 2.7–3.5 in offices, 4+ through dense structure
- 27.56
- Constant that reduces free-space loss to a one-metre reference
Worked example
With the default values below, Coverage Heatmap Estimator returns Cell Radius at Target RSSI of 12.6. Change any input above and every figure here is recalculated in your browser.
Inputs used
- AP EIRPaccepts -10–40 dBm
- 20 dBm
- Frequencyaccepts 400–90,000 MHz
- 5,500 MHz
- Target RSSI at the cell edgeaccepts -95–-40 dBm
- -67 dBm
- Walls between AP and cell edgeaccepts 0–10 walls
- 1 walls
- Loss per wallaccepts 0–30 dB
- 5 dB
- Shadow-fade marginaccepts 0–30 dB
- 5 dB
- Path-loss exponentaccepts 2–5
- 2.7
- Floor area to coveraccepts 10–500,000 m²
- 1,800 m²
Results
- Cell Radius at Target RSSI
- 12.6 m
- Effective Area per AP
- 327 m²
- Access Points to Cover the Floor
- 6
- Usable Link Budget
- 77.0 dB
- Cell Size Assessment
- Typical enterprise cell size
Step by step
- 1Values used
- 2Coverage Heatmap
- 3Cell Radius at Target RSSI= 12.6 m
- 4Effective Area per AP= 327 m²
- 5Access Points to Cover the Floor= 6
- 6Usable Link Budget= 77.0 dB
- 7Cell Size Assessment= Typical enterprise cell size
Assumptions and limits
- The result is derived only from the 8 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 1 decimal place, 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 is Coverage Heatmap calculated?
PL(d) = 20·log10(f_MHz) − 27.56 + 10·N·log10(d_m), inverted for d at a link budget of EIRP − target RSSI − wall losses − fade margin. The one-slope indoor model anchors path loss at a one-metre reference and then grows it by 10·N decibels per decade of distance. Solving it for distance at the point where received power equals the target RSSI gives the cell radius; multiplying the circle area by 0.65 accounts for overlap and non-circular real-world cells.
Why does Coverage Heatmap matter?
Predictive designs live or die on the path-loss exponent and wall losses — assume free space indoors and you will deploy half the APs you need, then re-survey after go-live.
What values do I need to enter?
This calculator takes 8 inputs: AP EIRP, Frequency, Target RSSI at the cell edge, Walls between AP and cell edge, Loss per wall, Shadow-fade margin, Path-loss exponent, Floor area to cover. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.