How Big is My Medieval City?

Have you ever wondered how big your medieval community should be? As in, how long does it take to circle the walls? How long to run across? How thinly spread are these archers on the walls? I was wanted this for a game the other day, and found a scholarly article on the subject.

We now have an equation, and tables:

LN(Area in Hectares) = A + B*LN(Population)

A and B are typically -2.25 and 0.75, respectively
LN is the natural Logarithm

Since calculating Natural Logarithms is a pain even with a calculator, I broke out the numbers into a table:

Population	Area	Width (Meters or Yards)	Width(Miles)	Rooms per Capita
2,000	30 Ha/ 75 Acres	500 meters	0.33	13.5
3,000	40 Ha/ 100 Acres	600 meters	0.38	12
5,000	60 Ha/ 150 Acres	750 meters	0.46	10.8
7,000	80 Ha/ 200 Acres	900 meters	0.53	10.3
10,000	110 Ha/ 275 Acres	1,000 meters	0.63	9.9
15,000	140 Ha/ 350 Acres	1,200 meters	0.7	8.4
20,000	180 Ha/ 450 Acres	1,300 meters	0.8	8.1
30,000	240 Ha/ 600 Acres	1,500 meters	0.9	7.2
50,000	350 Ha/ 875 Acres	1,900 meters	1.1	6.3
70,000	450 Ha/ 1,100 Acres	2,100 meters	1.2	5.8
100,000	590 Ha/ 1,500 Acres	2,400 meters	1.4	5.3
150,000	800 Ha/ 2,000 Acres	2,800 meters	1.7	4.8
200,000	1000 Ha/ 2,500 Acres	3,200 meters	1.9	4.5
300,000	1350 Ha/ 3,400 Acres	3,700 meters	2.2	4.0
500,000	2000 Ha/ 5,000 Acres	4,400 meters	2.6	3.6
700,000	2600 Ha/ 6,400 Acres	5,000 meters	3.0	3.3
1,000,000	3300 Ha/ 8,300 Acres	5,800 meters	3.5	3.0
1,500,000	4500 Ha/ 11,300 Acres	6,700 meters	4.0	2.7
2,000,000	5600 Ha/ 14,000 Acres	7,500 meters	4.5	2.5
3,000,000	7600 Ha/ 19,000 Acres	8,700 meters	5.2	2.3

Now, these tables are nice to have and all, but they're not going to be exact. They're mostly here to give a ballpark numbers you can tweak up or down to fit your city.

Two Thousand?

You may notice that the table starts at 2,000 people. This feels very small to modern observers, but such small hubs were considered towns, and the people in them towns-folk. Towns were a good deal smaller for most of history, and the truly huge cities tended to be rare exceptions that ruled their countrysides. City size also appears to have a strong cultural element: cities in Europe swelled in size  in the 13 and 14 hundreds, despite the total population of the area growing less than 20%.

City Shape

The width of these cities is actually calculated for a square city. Very few cities are square, with roundish shapes being common, but flattened blobs pushing up against a water way being another popular "design". Constantinople is shaped like a triangle, because that's the shape of the peninsula its on. Flattened blobs can multiply the width by 1.5 to get the length of the city and divide by 1.5 to get its depth (or more, for a really elongated community).

Rooms per Capita

I gave the density in terms of "Rooms per Capita". This term deserves some explaining. The "room" here is a approximately a 10 foot by 10 foot space, the size of a modest modern bedroom, or 100 square feet. I find that most people (including myself) have a poor understanding of what people per square mile, kilometer, acre or hectare actually means, so I chose a unit of area we do grasp: a modest room. 

Lest we think that 10 rooms per person is spacious and wonderful, let us remember that this includes the outdoors as well as the indoors, and spaces for commerce, storage, and animals as well as sleeping and cooking. It includes the road outside outside of homes, the shop, the workspace, the granaries, the local well, the marketplace, the walls, the city hall, the docks, and extra space for those wealthy Burghers who can afford it, not to mention their horses.

It doesn't take into account multistory buildings, which are a prominent feature of historical cities, so that adds some space for the poor souls crammed into major metropoli.

Density and History

Historical Cities did not spring up or die over single generations. Rome wasn't built in a day, and more importantly, Rome lasted long beyond its peak population. Many cities will have their fortunes wax and wane, varying their populations by huge amounts. Constantinople would bounce back and forth between 100 thousand and 500 thousand, and more if you use less conservative estimates. Cities could have other factors that just made them more or less dense. You can tweak the numbers up and down to account for this: the table is just a guide. 

Extrapolating Upwards

I'm most confident in these numbers for Western European cities in the 1300's, between the 2,000 number and the 200,000 number, because that's what the paper this is based on covered. The really big cities are just an extrapolation, and I expect the numbers for million+ cities may be off. The cities get even more dense, if my cursory look at Constantinople is a good indication.

Running the Game

I hope you remember this table next time your PC has to run across or out of the city! I hope you find it fills out your worlds, and I hope you find it useful.