Drawing Custom Population Polygons

Tom Forth’s Population around a Point is one of those wonderfully simple map tools that instantly invites exploration. Click anywhere on the map, choose a radius, and it estimates how many people live within that circle. Under the hood, it uses the Global Human Settlement Layer (GHSL) population grid for 2024, querying population points stored in a massive SQLite database.

Now, a new map expands this simple concept beyond circles. How Many People Live Inside? lets you draw free-hand shapes directly onto the map to estimate the population within any custom area. That extra flexibility dramatically changes the kinds of questions you can ask. Rather than "How many people live within 15 km of the station?", you can investigate: "How many people live inside the Thames Estuary?", "the LA basin?", or even "this oddly-shaped coastal strip?"

The new map utilizes the 2025 WorldPop Global2 database. Like GHSL, WorldPop provides gridded population rasters, but this project is designed specifically for custom-area analysis. This allows How Many People Live Inside? to dynamically identify only the raster tiles intersecting the user’s polygon before calculating a population estimate. For very large areas, the tool automatically switches to a lower-resolution 1 km workflow to maintain performance.

Like Tom Forth’s original map, the site is refreshingly honest about its data. These are not official census counts, but modeled population estimates derived from raster datasets. Consequently, the results are best viewed as informed approximations rather than precise totals - especially for rapidly changing urban areas or irregularly drawn boundaries.