Mega-Tutorial on worldbuilding Medieval Towns, Cities, Population, Professions, Armies, Technology, Justice, and Trade!
Better version on my blog here: https://buildkingdoms.wordpress.com
More info, more sources, better formatting.
Here I will lay out some very general guides for worldbuilding a medieval country. Mostly these are based on real world numbers and historical precedent, but I give them in the spirit of a worldbuilder, not a historian, meaning these are jump off points for your inner muse, not hard and strict *rules* that must be followed. The medieval world was rife with disease and plagues, but if you don't want to include them in your world, simply forget about them. You can tweak and add as much or as little importance to it as you wish. You will no doubt be able to find exceptions and contradictions for everything I say, that's great. Scrutiny, criticism, suggestions, contradictions, and questions are highly encouraged!
**Table of contents:**
#1 Towns and cities
#2 Population and land
#3 Health
#4 Professions
#5 Armies
#6 Technology, Crops
#7 Justice
#8 Trade, Travelers, Distance
#9 Conclusion
##**#1 Towns and cities, population distribution**
Let's talk about setting for a medieval fantasy world. Who are the people in the background? Where do they live? What kind of lives do they lead? Is it country side, or is it within the boundaries of the Evil Empire's capital? What is a capital? How many people live there? After all, armies that number in the hundreds of thousands do not make sense if the nation is comprised of nothing but sleepy little hamlets and the king's castle.
Fantasy and historical fiction often overestimate urbanization to an absurd degree compared to real life. But I get it, we want Gondor! We want King's Landing! We want wondrous capital cities to get lost in! We want our dashing rogue to steal a priceless treasure and vanish into the crowds!
Let's start small and build up. From farms. Farms are everywhere in medieval times. Literally everywhere! Ever inch of farmable land will be farmed. Because why wouldn't it be? (There's probably a lot of reasons, but you're in charge of those!)
So, you're looking at population densities of 30 people per square mile to 120 per square mile, over the entire landmass, depending if you're trying to grow wheat from rocks, or your land has rich, beautiful, life giving soil blessed by the goddess Ceres herself. Probably can even go more dense than that if your people have invented anything more efficient than a hoe (europe struggled to do this up until very recently).
If you have several families each farming adjacent to each other, it's probably in their best interest to build their houses together for safety and convenience. This is what you can call a village or a hamlet. **Villages consist of 50-1000 people**, and there are THOUSANDS of them in any given country. When you have people clumped up like this, it will make sense to start distributing labor and specializing. Your nephew will go full time into brewing alcohol, I don't know what he puts in it, but his IPA is off the chain, and your brother in law's uncle always made the sturdiest horseshoes, and so we built him new smithy right in the center of the village so he can supply all of our horseshoes (actually don't do that-- that's a fire hazard).
Now, what sets apart your village from the next village is the location. Location, location, location. While most villages have to build wells and travel to get to the nearest stream, your village is built right next to the river. That makes it easy to raft up and down for transportation, to fish, to collect water, and to defend if need be. Soon other families in the area, marveling at your ability to brew beer and make horseshoes, start visiting and relying on your village as a place for trading, for drinking, for celebrations, and for safety, even if it means they have to travel a little. Soon you start intermarrying, and what do you know, your brother in law's uncle's new wife's cousin is a basketweaver. So we build him and his family a place right next to the smithy to weave all of our baskets. Suddenly there's a lot more new faces around here, and the new baskets are the talk of the *town*. **Town Population: 1000-8000**
Your town is now bustling, you have inns and cobblers (they make human shoes), a marketplace, roads, merchants travelling through your roads to go to the marketplace to buy your shoes and beer, and even a clown! Smaller villages from all around will travel to the town to sell their surplus foods and crafts. Then you have people that cater to travelling merchants and craftsmen, after all, travellers need food, animal feed, new shoes, wagon wheels, etc. But since it has a reputation of being such a great place to live, the people decide, hey, why not build a wall, maybe a castle even, that way no roving band of assholes can decide it'd be a great place for *them* to live instead. Suddenly, you find yourself living in a city! In the entire country, there's only a dozen of places like it. **City Population: 8000-12,000.**
In a city, you will begin to see things like walls, castles, universities, government buildings, and palatial estates, probably out of stone, rather than wood. Remember, hygiene is going to be way more important than before, unless your setting calls for plagues-- immigrants will have to replenish your city's population because you worldbuilded a culture of public defecators.
Any bigger, and you become a big city, or a capital, maybe just one or three like it exist in your country. Population: 12,000-100,000. These are places like Venice, London, Paris, Florence, Milan, Naples.
Is this as big as it can get? 100,000? No! Tenochitlan reached 250,000, Constantinople reached 500,000 souls, and China laughs at your accomplishments. Again, hygiene or plague!
Castles. While largely up to you and your culture, a good rule of thumb is one castle/large fortification/citadel per 50,000 people. You can find these in a city, in large towns, and/or wherever nobles have carved out their territory. Of course, for small folk in small villages and towns, they will have their own fall-back shelters to protect them against raids, these can be the local church, monastery, abbey, a stone administrative building, they could forts, wooden palisades , small stone keeps. There will be thousands of such structures in any country. Having plenty of border forts is a very good idea as well. Also why not throw in some bandit fortresses and goblin lairs ?
##**#2 Population and Land:**
Let's back out now and get some perspective on the country as a whole. We need to know how big it is, and how many people are in it. There are two ways to do this, working *up* from arable land, working *down* from population.
To skip this section and its explanation, simply go to [This website and use their calculator.](http://donjon.bin.sh/fantasy/demographics) It's all based on [this amazing website anyway](http://www222.pair.com/sjohn/blueroom/demog.htm).
First, here's the important part. **Just because I said you have an AVERAGE population density of up to 120, that does not mean that's how many people live in a square mile.** That's just how many live when spread *over the landmass*, including mountains and rivers. People don't normally live on mountain peaks or in rivers. **It also does not mean that's all the land is able to *support*.** The farms should produce surplus, and to see how many people that 1 square mile of developed land can *support*, let's use a number between 50-300, bad, rocky farmland plagued with endless misfortune on one end, great farmland in the magic kingdom on the other. You can also have a stupidly low number in the case of subsistence farming, tundra plains, or worse, population decline leading to ghost towns. But let's go down the middle, 180. (I personally like it higher, but let's roll with 180).
Let's make our landmass 100,000 square miles. That's 75% of Germany, 120% of Great Britain, 50% of France.
The first way: If you know how much of the kingdom's geography is arable, good, skip this. If you don't, let's say blankly that there is 5 million people in our hypothetical kingdom. In 1600, Great Britain's population was 5.5mil and Germany 10mil. Sounds fair. So let's divide the population by 180. You get 27,777 square miles. So almost 28% of the land in our kingdom is arable. Wow, That's pretty poor, right? Great Britain looked like this, with most of its population in huddled in the south of england.
The second way: Let's say I want 50% of my kingdom's land arable. With 180 people per square mile of farmland, I get 9 million people. That's a lot happier!
As for urbanization, let's arbitrarily say we have 3 giant cities, population of 100, 75 and 50 thousand respectively. And arbitrarily adding 12 cities averaging 10,000 each, then 8 times as many towns as cities, averaging 4500 each. All together, I end up with 885,000 people living in 111 towns and cities. That's roughly 1 out of every 10 people. And I have about 180 castles.
Anyway, these numbers *are yours to play with*. If you want a kingdom the size of Russia, with 1 million people in the capital (or way more!), 20 metropolises, and farmland supporting 400 people each square mile, I support it! Remember, these are averages and maximum population densities on developed land. You will have plenty of room to add desolate regions within the country and leave room for growth in underdeveloped land.
I'll just add some ranges for some reference.
2-15 cities seems pretty feasible, and there's no reason you can't have several large, several midsized, and several small ones. Just think about whether there's something, either a crossroads, a river, a shoreline, an artifact, a huge gold mine, anything that will justify the city being there. x2-18 times as many towns as cities. x2 is what you would have seen during the dark ages, x18 is what you saw on the cusp of the renaissance.
##**#3 Birth Rates, Mortality, Dental Plaque, and Plagues**
What's very important to note is the health of your population. That is if you're getting in the nitty gritty. Skip this section if you don't intend on describing medieval shithouse etiquette, or you have widespread healing magic.
It's often repeated that life expectancy was 30 years in more primitive times. This is extremely misleading and you need to know why! The biggest factor throughout history has been infant and child mortality, bringing the average life expectancy way, way down. For example, if half the population dies before the age of five, but everybody else dies at exactly 70 years old, the *average life expectancy will be about 36 years*, while about 25% of the population will be between the ages of 50 and 70! This is mostly due to poor access to medicine, if there was any at all, and if your doctors washed their hands after handling corpses and before delivering a child (they didn't).
This is why your medieval society will probably place an emphasis on having many children, for more help around the house, more children to take care of you in old age, or maybe it's part of their religion. Or conversely, an advanced civilization may be entering into an era of decline, with child-rearing being too draining on the independence of its wealthy and leisurely citizens. City life alone may cause a drop in births, as women and men might be too busy plying their trade to have many children. Bonus to low medieval birth rates if you have access to birth control, like [Silphium](https://en.wikipedia.org/wiki/Silphium)!
Other factors that lower birthrates are wealth, education, female labor participation, urban residence, education, increased female marriageable age. Could be useful for your society or just on a character-by-character basis. Also, [Silphium](https://en.wikipedia.org/wiki/Silphium)!
For those that live in cities, hygiene is very, very important! Shitting in the streets, dumping the dead in the river, lack of public bathhouses, no garbage disposal system, and overcrowded dirty apartments are great for plagues and diseases, but not your citizens!
Anyway, say you have some settlers moving to some huge, newly-discovered continent. How long until they can repulse an invasion from the Evil Dragon Empire? Let's do some numbers. The global average birth rate is about 20 births per 1000 people per year, but plenty of developing nations are going to range anywhere from 25-50/1000 (it was 30 during the baby boom years). As for mortality, this is going to largely influenced by infant and child mortality, hygiene, and access to medicine. Historically, you're looking at around 20-40/1000. If you wanted to chart the population growth over the years, use the equation:
Starting population*((1+(b-d))^years)
Plug your birth rate as b and mortality rate as d in decimals. For a pretty ridiculous example, with b=.032 (that's 32 births per 1000 per year, or 3.2%) and d=.010, you'll end up with a population of 6.8 million, giving you roughly the population of great Britain in the 16th century in just 300 years, starting with a population of 10,000. (just by replacing b=.04, your population will jump to 130 million!) So add disasters, plagues, famines, or godly good health and fortune as you like to adjust the numbers how you want!
##**#4 Trades, Tradesmen, and Trading**
Okay, so with this many people running around, what do they actually do?
Well these two resources have some good tables on what professions to expect in an average town. [Ctrl-f "Merchants and Services"](http://www222.pair.com/sjohn/blueroom/demog.htm) or [examine a very thorough list look here.](http://arcana.wikidot.com/list-of-medieval-european-professions)
Up until very recently the vast majority of people were farmers living in the countryside. The efficiency of different agricultural techniques and technologies can allow for the division of labor to become a lot more broad. Essentially you have a sliding scale, from 9 farmers to every 1 tradesman at the most inefficient end (1790s America was here), all the way down to something like 7 to 3 tradesmen on the other (that's better than Rome at its apex), going any further puts you near the limit of the medieval and ventures into the industrial age. Or maybe you just import most of your food.
Let's do some numbers down the middle with 8:2. Which makes sense with the hypothetical kingdom we built above. Remember, we had 1 in every 10 people in a town or city. Having the rest spread out across a bunch of small villages and towns makes sense. Imagine if every small village of 200 had 20 dedicated tradesmen, 40 if you include their spouses. If you say they have two children each, that 80 people not farming in a single village. Still not unimaginable if you consider a square mile supporting 180 people, but maybe it's not ideal for you circumstances. Children will typically be their parent's apprentices, and they will have several. Unless your society is more individualistic and schools are a thing.