Snagglefjord

[Tancread]

Medieval Demographics Made Easy

Be sure to check out the Calculators and Spreadsheets bit at the very bottom of the page.

That's a very useful site. Sets good baselines to use anyways. One problem with fantasy is of course it could completely screw everything up. Lets say there is common magic that doubles the crop yield per acre or some such. That sort of thing plus constant monsters in an area is bound to cause changes to the demographics in pretty unpredictable ways.

[Midgardsormr]

Quite true. Unfortunately, though, I have yet to run across credible census data from a magical realm!

It should also be noted that these guidelines represent England at a particular time (11th century, if I recall correctly). It should be adjusted if the society being modeled has better or worse technology (or equivalent magic).