The other day I was talking with a friend about population density and the number of people who live on the ocean. So I did some research on the numbers, and here are the results.
USA
Total Area = 9,833,520 km² (3,796,742 square miles).
Population = 331,893,745 (2021 estimate).
Population Density = 33.6/km² (87/square mile).
All Land on Earth, including deserts and glaciers
Total Area = 148,326,000 km² (57,268,900 square miles).
Population = 7,795,000,000.
Population Density = 52.6/km².
Oceans
Total Area = 361,900,000 km².
Population = 100,000 estimated*.
Population Density = 0.00028/km² or 1 person per 4000 square kilometers.
* = (There are no hard statistics for how many people live on the oceans. There is estimated to be twenty to thirty thousand cruising boats in the world. If we average 3 people per boat, that gives us sixty to ninety thousand people. As such, this is a generous estimate. But even if my numbers are off by a factor of 10, if there's actually 1 million people living on the oceans, it would still be 1 person per 400 km²).
Comparison
To relate that density to the USA, it's the same as if the entire USA had a population of 2,500 people.
If you related that to the entire planet, it's like the Earth's population was 41,500 people.