Question about villagers and 1 acre

[MillySoSilly]

I tried to find the thread where someone commented about "X" amount of villagers can live in one Acre of land. I'm not sure if this is true or not. Does anyone know? Right now I have 5 villagers in one acre with no Pwp's. I think one acre is 16x16, is that also correct? Let me know!
Thanks!