Free tool · radius map
Draw a radius on a map.
Search an address, city or ZIP, pick a radius, and see the circle with its area and diameter. A geofence is exactly this: a line on a map that alerts you when a vehicle crosses it.
A radius covers square miles.
Diameter ( in area).
Area = π × radius². Diameter = 2 × radius. Flat-map arithmetic; for circles under 200 miles the Earth's curve changes it by less than 0.1%.
Your circles
No circles yet. Pick a center and a radius, then draw.
| Circle | Center | Radius | Diameter | Area | Actions |
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The share link holds the circles themselves (centers, radii, names). Nothing is saved on our side.
Is this address inside the circle?
The same question a geofence answers every few seconds: is the vehicle inside the line or not.
Distance = straight-line (great-circle) miles from each circle's center, haversine formula.
What is a geofence?
A geofence is a circle (or any shape) drawn on a map around a place you care about. A GPS tracker in the vehicle reports where it is; when that position crosses the line, in or out, the system sends you an alert.
The circle you drew above is the whole idea. A tracker just watches it for you, all day and all night.
Three common uses
- Service area. Draw the radius you quote jobs in. Know when a truck goes outside it, and how far.
- Delivery zone. Set the edge of where you deliver for a flat fee. Anything past the line is a different price.
- After-hours yard alert. A small circle around the yard. If a vehicle leaves it at night or on a weekend, you get a text.