Draw a Radius on a Map
Click the map or search an address to set a centre, type a radius in miles or kilometers, and draw up to five circles at once -- each with its area, circumference and a shareable link, all computed live as you edit.
Search powered by OpenStreetMap Nominatim, limited to one lookup per second. Didn't find it? Click the map instead.
Click anywhere on the map to move the highlighted circle's centre. Map data © OpenStreetMap contributors.
What a geodesic radius circle actually is
A radius circle on this tool is a geodesic circle: the set of every point on the Earth's curved surface that is exactly your entered radius away from the centre, measured along the surface (a great-circle distance), not through the Earth or across a flat map. That distinction matters more than it looks -- a flat-map circle drawn with a fixed pixel radius would represent a different real-world distance at every latitude, because the Web Mercator projection this map uses (like almost every web map) stretches east-west distances as you move away from the equator to keep north pointing up on screen. A geodesic circle is squashed into an oval-looking shape by that same stretch at high latitudes, but the real-world radius it represents -- and the area and circumference figures below it -- stay exact regardless of where on the map you draw it.
Area and circumference are computed with the ordinary flat-circle formulas, area = πr² and circumference = 2πr, applied to your entered radius. That's an extremely close approximation for any radius you'd realistically draw here (a delivery zone, a commuting range, a few hundred miles at most) -- the Earth's curvature only meaningfully distorts a flat-circle-area formula at radii approaching thousands of miles.
Worked examples
Two radii worked by the tool's own formulas, area = πr² and circumference = 2πr -- checked against hand-derived values in the site's own test suite, not just typed here.
| Radius | Area | Circumference |
|---|---|---|
| 10 mi | 314.2 mi² | 62.8 mi |
| 25 mi | 1,963.5 mi² | 157.1 mi |
Draw a 10-mile circle above and its own card will show this exact area and circumference figure.
Frequently Asked Questions
Is the circle drawn as a true geographic radius, or just a flat pixel circle?
It's a true geodesic circle -- every point on its edge is the entered radius away from the centre, measured along the Earth's surface, not just the same pixel distance on your screen. The map tool draws it with Leaflet's L.circle, which handles that geodesic math directly, using the radius you enter converted to meters.
Why does a circle look squashed or oval on the map, especially far from the equator?
That's the map projection, not the circle. Web maps (this one included) use the Web Mercator projection, which stretches east-west distances more and more as you move toward the poles to keep north always pointing up. A true geodesic circle of, say, 50 miles is a perfect circle on the actual Earth's surface -- the projection just draws that circle wider than it is tall on your screen at higher latitudes. The circle's radius, area and circumference numbers are still exact; only its on-screen shape is stretched by the projection.
Can I draw more than one circle at once?
Yes, up to five, each with its own colour, centre and radius. Click a circle's card in the list (or click "+ Add circle") to make it active, then click the map to move that circle's centre -- the highlighted card and the bold outline on the map always show which one you're editing.
How do I share a radius I've drawn?
Click "Copy shareable link." Every circle's centre, radius and your chosen unit (miles or km) are encoded directly in the page's URL as you edit them, so opening that link rebuilds the exact same circles -- no account, and nothing saved on a server.
Where does the address search come from, and what if it doesn't find my address?
Address search uses OpenStreetMap's free Nominatim geocoder, rate-limited on our end to one lookup per second per its usage policy. If it can't find an address (rural routes and very new addresses are the most common misses), click the map directly, or use "Use my location" if you're already there.
Does the radius account for roads, terrain or travel time?
No -- this is a straight-line ("as the crow flies") radius only. A 10-mile circle means every point on its edge is 10 miles from the centre in a straight line, not a 10-mile drive. See the Distance Between Two Points page for more on why driving distance is almost always longer.
Every distance, area and radius on this site is a geometric estimate from the coordinates you provide, not a survey-grade measurement -- and this tool does not calculate driving routes or travel time. See the Terms.