Sensor Network Density Calculator
How many sensors an area needs at a given range — with the overlap a reliable network requires, and the spacing between them.
A sensor with range r covers a circle of area πr².
How the sensor network density calculator works
A sensor with range r covers a circle of area πr². Dividing the area by that gives the theoretical minimum, but circles do not tile: real networks need about 20 to 40% overlap to leave no gaps and survive a failed node.
The practical spacing for a hexagonal layout is about 1.7 times the range — the number a surveyor actually uses.
Formula: sensors = area / (π r²) × (1 + overlap)
Worked examples
| Inputs | Sensors needed | Note |
|---|---|---|
| 18 km² at 250 m | 120 | about 120 sensors |
| No overlap | 92 | the theoretical minimum — with gaps |
| Long-range sensors | 30 | a quarter as many |
FAQFrequently asked questions
Why do I need more sensors than area divided by coverage?
Because circles leave gaps when tiled, and a network that fails when one node fails is not a network. Twenty to forty per cent overlap is standard.
What is the spacing in a hexagonal layout?
About 1.73 times the range — root three. It is the densest arrangement that still covers every point.
What range do city sensors have?
Air quality and noize sensors represent about 100 to 300 m; LoRaWAN gateways reach kilometers; traffic sensors are point measurements.
Does terrain matter?
Enormously for radio range and line-of-sight sensors. Treat the range as an effective figure for the area, not the datasheet number.
What dominates the cost?
Installation and ongoing data and maintenance, not the sensor. A cheap sensor with an expensive site visit is not cheap.
Where these figures come from
- UN-Habitat — Urban Indicators Guidelines — density, green space and public space benchmarks
- World Health Organization — Urban green spaces — the 9 m² per person minimum
- ITE — Parking Generation Manual — parking demand rates by land use
- US Census Bureau — Population and housing — the US national statistics agency
Last checked: September 2026. Default per-capita rates are mid-range figures from national statistical agencies and utility reports; every one is an input you should replace with the local figure.