I'm going to disagree here.
God said to "replenish the earth," which means to "fill it up."
Science yells "overpopulation" ... well ... for reasons.
But the fact is, 95% of the world's population lives on just 10% of the land.
The acreage isn't the primary concern when it comes to population size concerns.
A) location/logistics
The total land surface area of Earth is about 57,308,738 square miles, of which about 33% is desert and about 24% is mountainous. Subtracting this uninhabitable 57% (32,665,981 mi2) from the total land area leaves 24,642,757 square miles or
15.77 billion acres of habitable land.
So, that would be 2 acres of land per person currently on the planet. Now, we also need to use some of that land for agriculture and farming and livestock. We also need to use some of that land for means of transportation (roads, bridges, etc...) There are also some communal resources (which we all enjoy) that require land. (Supermarkets, military bases, museums, libraries, office buildings, etc...) So that's not really leaving people with the "spacious spread" people are thinking.
B) resources
Even if we pretended that the things listed in bullet point A were not a factor, simply having enough land doesn't equate to have everything else you need. And there would be a land requirement in order to scale up to a new (bigger) population sizes...more people means we need more stores, more farmland, etc...
C) social/cultural challenges
Absent the taring down of national borders and sovereignty, how does one handle the allocation? According to recent estimates, there's about 630 million acres of unoccupied and unused land in the US. They're packed in like sardines over in places like China and India. If we went 1 person per 2 acres of available land to space things out a bit, you comfortable with importing 300 million foreign nationals from China and India to even out the load a bit so that the population densities aren't so high in those countries? (Not to mention, many from those countries wouldn't want to relocate here for the same reasons you probably wouldn't want to relocate to a different country with completely different cultural norms - and climate - than what you're used to)
So it's not just as simple as a "divide acres by population, and see! we've got plenty of room" math exercise.