I'm running a premodern setting where the characters will be involved in local administration. Assuming no magic, how many farmers does it take to support one non-farmer? Any statistics/estimates are welcome, from neolithic to renaissance (but preferably between Roman and medieval). A perfect answer would be something like this:
In the Vth century, W farmers could farm X acres of land, growing enough of crop Y for themselves and Z other people.
Perfect accuracy isn't my goal here, I'd just like to get the result close-ish. It's like when you have a soldier or a mining engineer playing your setting — you don't have to get the combat or the mining correct, just not so awful that it gets laughed at.
Best Answer
From the ever-essential Medieval Demographics Made Easy, I find that:
From Medieval Manors I learn that a single peasant farmer worked 20-40 acres of land, so let's settle on 30 acres.
From Google, I learn that 1 square mile is 640 acres, so that square mile that could support 180 people means about 21 peasant farmers worth of land in a square mile.
Now, it has to be understood that these farmers weren't just lone bachelors, tirelessly working the land. So let's say that each peasant farmer is assisted by and supports a family of what...4? 5? So that means that this square mile of land is supporting 84-105 people just to get its production out. That leaves roughly 80 - 100 other people this land was capable of supporting.
So to answer your question in round terms:
Obviously, not every inch of land will be arable, and there's a sort of hierarchy of non-agrarian types between the farmer and a wealthy noble or city dweller. But this should
A) Get you close and
B) Give you some good resources to consult for more details.
Also check out some of the other answers in realm-management.