Draw a polygon anywhere on the Earth and Population Explorer will provide an estimate of the population within the defined area. I’ve tested the tool by selecting areas that I know, such as London and the UK, and I’ve also tested it by searching for estimates in deserts and the sea. From my limited testing Population Explorer does seem to return accurate population estimates.

The results of each search displays the total population, the population density, the number of males & females, the age structure of the population and population growth estimates.