Geofence Circle Area Calculator
A circular geofence is set by a centre and a radius. Knowing the area it covers helps you size triggers, estimate population or asset coverage, and compare zones. Enter the geofence radius in metres to get the area in square metres, square kilometres, hectares and acres, plus the boundary circumference. The calculation uses the standard circle formulas and treats the geofence as flat, which is accurate at app scale.
Geofence area formula
area = pi * radius^2
circumference = 2 * pi * radius
hectares = area / 10,000
acres = area / 4,046.8564224
The geofence is a circle, so its area and perimeter follow the standard circle formulas. Conversions to hectares and acres use the exact SI and international-acre definitions.
Worked example
Radius 500 m: area = pi times 500^2 = 785,398.16 m2 = 0.79 km2. That is 78.54 hectares or 194.07 acres. The circumference is 2 times pi times 500 = 3,141.59 m and the diameter is 1,000 m.
Geofence area: frequently asked questions
What is a circular geofence?
A circular geofence is a virtual boundary defined by a centre point and a radius. Location-aware apps trigger an action when a device enters or leaves the circle. The covered area is simply the area of that circle.
How is geofence area calculated?
Area = pi times radius squared. Circumference = 2 times pi times radius. These are the standard formulas for a circle. On the scale of typical geofences (metres to a few kilometres) the flat-circle approximation is accurate; Earth curvature only matters for very large radii.
How do I convert the area to acres or hectares?
One hectare is 10,000 square metres and one acre is 4,046.8564224 square metres (the international acre). This calculator reports the area in square metres, square kilometres, hectares and acres at once.
Does this account for the Earth's curvature?
No. It treats the geofence as a flat circle, which is standard for app geofences up to a few kilometres. For continental-scale circles you would need a spherical cap area formula instead.
Sources and references
- National Institute of Standards and Technology: unit definitions, acre and hectare.
- U.S. Geological Survey: geographic measurement reference.
- Formula: standard Euclidean circle area and circumference.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.