Hussar
Legend
We figured that it's lover than a modern big city, because of far less levels of the buildings. You also need room for the streets, maybe a park, market place, shops, a large palace and much more. Munich today has 4286 per sq km and a fair amount of sky scrapers. Therefore we just halved that for a wild guess that is accurate enough to stop the players arguing about it. And for my city I though about half-timbered houses which should no feature more than 3 levels in general.
I'll take a look at the City Designer and see if it works good enough to be worth it's price. I one tried Campaign Cartographer and it was a total button hell. You were unable to figure out how anything worked at all. And id didn't seem to support an evolutionary development like with layers and stuff. I was pretty disappointed for the "top notch tool".
Just to jump on the pile a bit here, something to remember about medieval cities is that you would generally have large numbers of people sharing a single room. Families would not have their own bedrooms unless they were very rich. You'd quite possibly have seven, eight people sharing a single bedroom that probably doubles as the living/dining room during the day.
I remember being shocked when I traveled to Angkor Wat and toured the Bayon - a city of almost a million people around 1100, one of the largest in the world at the time - and I could get around the ruins on foot. Sure, it took a couple of hours, but, you could walk across the city. When you don't need space for cars, streets become REALLY small.
Heck, ancient Rome wasn't exactly huge either IIRC.
I'd vote either Inkwell's city generator or the Cartographer's Guild. If you can't find a map that suits your purpose there, you're really picky.