Draw a radius circle on the map to measure coverage areas, signal ranges, service areas, proximity zones, and buffer zones around any location. The circle is a true geodesic circle computed via Turf.js (128-vertex WGS84 polygon) — not a flat Mercator-projected circle — so it stays geometrically accurate at any latitude. Radius, diameter, circumference, and area are all calculated using the Vincenty formula on the WGS84 ellipsoid (the same standard used by GPS), giving sub-millimeter theoretical accuracy. Moving the circle preserves the exact radius in km regardless of latitude. Note: the circle's shape may appear slightly different after moving to a new location — this is not a bug. It accurately reflects how a geodesic circle of the same radius looks on a Mercator map at a different latitude.
Click and drag on the map to draw a radius circle.
While dragging, a live tooltip shows radius, diameter, circumference, area, and center coordinates.
Drag the edge handle to resize — the handle stays in whichever direction you dragged.
Drag anywhere inside the circle to move it — the radius is preserved exactly.
Click a preset to jump to a common radius. If a circle is already drawn, its center is kept.
Type a value in the Radius input and press Enter to set an exact radius.
Click the edit icon next to Center to type new coordinates directly.
Switch units (km, m, mi, ft, nm) — presets update to match the selected unit.
Press Clear or Esc to reset.
Geodesic circle: Turf.js 128-vertex WGS84 polygon — accurate at any latitude
Vincenty formula (WGS84 ellipsoid) — sub-millimeter accuracy
Radius preserved exactly when moving the circle
Edge handle stays in the direction you last dragged
Preset sizes per unit (km, m, mi, ft, nm)
Direct radius input with instant unit conversion
Editable center coordinates
Radius, diameter, circumference, and area display
Real-time cursor tooltip during draw and edit