Population within a radius

Worked example: 25 miles around Columbus, Ohio

A 25 mile circle on the sphere covers 1,963 square miles. Centered on the Columbus capital point, it contains 35 places of 1,000+ people. The five largest are:

• Columbus, OH: 933,263 people, 1.7 miles from the center
• Dublin, OH: 49,456 people, 13.0 miles from the center
• Delaware, OH: 46,521 people, 22.8 miles from the center
• Grove City, OH: 44,019 people, 7.3 miles from the center
• Reynoldsburg, OH: 42,897 people, 11.2 miles from the center

Their populations add up to 1,475,694. The county method finds 5 counties with an internal point inside the circle (Delaware County, Fairfield County, Franklin County, Madison County, Pickaway County) with a combined 1,869,720 residents. The two totals answer different questions, as explained below.

Why there are two totals

The Census Bureau publishes population estimates for areas, not for circles. So any radius count has to decide which areas to include. This tool shows two answers side by side.

Place population adds the Vintage 2024 estimate for every incorporated place of 1,000 or more whose internal point is inside the circle. It misses people who live outside city limits, in unincorporated areas, and in towns under 1,000. It can also count a large city whose center is just inside the line even though half its land is outside.

County population adds the whole population of every county whose internal point is inside the circle. It covers rural residents but is all or nothing: a big county whose center sits just outside contributes zero, and one whose center is just inside contributes everyone.

For a small circle inside a metro area, the place total is usually the better guide. For a large circle across rural land, the county total is usually closer. When the two numbers are far apart, that gap is itself useful: it tells you how much of the population lives outside incorporated places in that area.

How the circle is drawn and measured

The circle is geodesic: every point on its edge is the same great-circle distance from the center. The area is the spherical cap on a sphere of radius 6,371.0088 km, so it stays accurate at large radii where a flat pi r squared would drift.

Each place is tested with the haversine distance from the center to its internal point. The list below the map is sorted by population and can be downloaded as CSV with the distance to each place.

Limits and alternatives

Census-designated places are absent because the subcounty estimates this site uses cover incorporated places only. The places file holds a single Hawaii entry, Urban Honolulu, because the state's other communities are census-designated places. Use the county total there.

A radius is not a travel time. If you need who can reach a site within 30 minutes, a drive-time polygon from the drive time map answers that better.

Choosing a radius

Area grows with the square of the radius, so doubling the radius quadruples the land inside. On the sphere, measured at 40° north:

• 5 miles: 79 square miles
• 10 miles: 314 square miles
• 25 miles: 1,963 square miles
• 50 miles: 7,854 square miles
• 100 miles: 31,414 square miles

Pick the radius that matches the question: a few miles for a neighborhood, tens of miles for a region. Large circles take in more unincorporated land, which only the county total counts, so lean on the county figure as the radius grows.