Presence Sensor Coverage Calculator

Calculator

Garden length (m)

Measured along the main walking direction.

Garden width (m)

Use average width for irregular shapes.

Sensor type

Different types vary by still-presence sensitivity.

Mount height (m)

Typical: 2.0–3.5 m for eaves or pergolas.

Detection angle (°)

120° is common for wall-mounted sensors.

Detection priority

Still presence reduces radius to avoid false comfort.

Overlap allowance (%)

10–25% helps cover edges and sensor falloff.

Obstructions penalty (%)

Plants, fences, posts, and uneven terrain reduce reach.

Tip: For L-shaped gardens, run multiple rectangles and add sensor totals.

Length (m)	Width (m)	Sensor type	Height (m)	Angle (°)	Overlap (%)	Obstructions (%)
10	6	PIR Motion	2.4	120	15	10
14	10	Microwave Motion	3.0	180	20	15
8	5	mmWave Presence	2.2	120	10	8
20	12	Dual-Tech	3.5	180	25	20
12	12	mmWave Presence	2.8	90	15	12

These rows show typical input combinations for outdoor spaces.

The calculator estimates an effective radius using a sensor preset, then scales it by mounting height and detection priority:

The effective coverage area is computed as a sector of a circle, reduced for overlap and obstructions:

angleFactor = angleDeg / 360
effectiveArea = π × radius² × angleFactor × (1 - overlap) × (1 - obstructions)

Finally, recommended sensors is the garden rectangle area divided by effective area, rounded up: ceil(gardenArea / effectiveArea).