I'm creating an rpg medieval setting, and I want it to feel pretty real. Castles make fun locales, so I'm trying to figure out how many castles I can plausibly cram into a 5,000 mi² region. The region is presided over by a Duke-like figure, who likely has some number of lesser lords underneath them. I assume all lords need at least a keep, but perhaps there are other additional castle needs.

My general question relates to the factors that determine how many castles will be in a given Medieval Setting. I can guess at some of the factors (population density, agricultural productivity, military defense needs) but what I'm looking for here are some real figures. What was the castle density of Medieval Europe? Where was this density high? Where was it low? Why?

There's a very nice answer here about the proximity of medieval towns to one another, but I wasn't able to turn that into an answer specifically relating to castles.

EDIT: Thank you for the input so far. The prevailing answer at the moment seems to be "you have as many castles as you have lords". I'm sure there are also as many castles as there are castle-courtyards, but that doesn't really help me very much. If # of castle = # of lords, what determines the number of lords?

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    $\begingroup$ First question: what's a castle? This sounds funny, but "castles" involve everything from earthenworks to that lovely sample of all castleness in Bavaria and made from everything from dirt to marble. There were castles that were ruins by the medieval period and castles yet to be built. So... what's a castle? $\endgroup$
    – JBH
    Commented May 3, 2018 at 20:46
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    $\begingroup$ This sounds like a better fit for History Stack exchange $\endgroup$
    – bendl
    Commented May 3, 2018 at 20:55
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    $\begingroup$ Also, the medieval period was a 1,000 year period. That's a lot of time with a substantial architectual and technological difference between start and end. Can you pick a specific reference date? $\endgroup$
    – JBH
    Commented May 3, 2018 at 21:31
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    $\begingroup$ Sure. Click the flag link under your question, choose "in need of moderator attention" and explain the issue in the dialog box. Or, you can respond to James' answer with the request, that diamond next to his name identifies him as a moderator. Or, still, you could simply edit a big header on the question that says "WAIT! PLEASE DON'T ANSWER, I'M IN THE PROCESS OF MAKING EDITS!" Which will also be a great measure of how many people are paying attention. 😁 $\endgroup$
    – JBH
    Commented May 3, 2018 at 22:14
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    $\begingroup$ Well, does the setting have magic or not? Because the right kind of magic would make castle construction a lot easier, and thus would likely result in more and/or larger castles. $\endgroup$ Commented May 3, 2018 at 23:28

4 Answers 4


So we have a duchy of some 5,000 square miles, or 14,000 square kilometers, some 120 km by 120 km, which makes it about one third the size of the medieval Duchy of Bavaria or about one fifth of the modern Free State of Bavaria. Wikipedia has a great list of 627 castles in Bavaria (by which they mean the modern state); pro rata this results in some 100 to 110 castles in the hypothetical duchy in the question.

A "castle" is a very ambiguous thing. There at least three kinds of "castles" in European history:

  • The purely utilitarian military constructions, where nobody wanted to live if he was not paid for it. Their purpose was to defend important points, such as a river crossing, a mountain pass, a major crossroads and so on. Those were the most expensive military weapons platforms of the day -- if the dukedom is rich, there will be plenty of those, and if the dukedom is not so rich there will be as many as they could afford. Don't forget to add a small castle to any toll-collection point.

  • The combined fortress and residence castles, where the duke and his counts lived. Those are of course fewer, and larger, and more confortable, and had actual inner courts. In the small duchy in question there may well be anything from half a dozen to maybe a dozen and a half of those, depending on the specifics of your duchy; Bavaria, to continue the example, is full of mountains so there were more residential fortresses than usual. The dukes will maintain multiple residences, so that they can divide their time between the various parts of the land, e.g., there was the Duke's Castle ("Herzogskasten") in Ingolstadt, the Trausnitz Castle (what the dukes called home), Dachau Palace etc.; then the counts or marquesses which ruled over the counties or marks will each have their own fortress-residence.

  • Then there are the purely residential "castles" which were really strongly built large houses. Each noble family will have one of those.

Depending on the particular setup, there could also be a set of royal or imperial castles, not subordinated to the duke.

Then one must not forget the walled cities. This is the Middle Ages, and any city worth its charter will want to build walls. For example, in Bavaria, Bamberg, Ingolstadt, Nuremberg, Passau, Rothenburg, Würtzburg, etc. Each will have a fortress, and also a town hall which may well resemble a miniature castle...

As @Kingledion suggested, I should add that during the modern period there was a time, say from about 1700 to 1850, when rich aristocrats built follies and non-functional castles for pleasure. Compare:

The New Castle in Ingolstadt   Nueschwanstein Castle

On the left, the New Castle in Ingolstadt; this is a real late-medieval castle. On the right, Neuschwanstein Castle; this is a modern 19th century palace built by Ludwig II of Bavaria as a sort of overpriced country retreat. Hint: one of them looks similar to the Disney castle, the other doesn't.

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    $\begingroup$ This is a superb answer, and has given me some really great leads for my research. Thank you! That is waaay more castles than I thought. I was under the impression there would be like 5 or so stone structures and a lot of little wooden forts, but I'm finding that Dutchies 1/5 the size of my setting can have dozens and dozens! cornwall-calling.co.uk/maps-cornwall.htm/castles-cornwall.gif $\endgroup$ Commented May 4, 2018 at 0:08
  • $\begingroup$ Important to point out that not all castles were in use at the same time. The earliest 11th century stone castles do not have the same form or function as Neuschwanstein, which has more in common with Disneyland than a functional medieval castle. Surely some of the 600 were ruined by the 1300s, etc. I would revise that castle estimate downwards. $\endgroup$
    – kingledion
    Commented May 4, 2018 at 12:03
  • $\begingroup$ @kingledion: Added some words to the answer to explain the difference between a medieval castle and an early modern folly. $\endgroup$
    – AlexP
    Commented May 4, 2018 at 12:33
  • $\begingroup$ Pretty good answer, just to add castles are big military assets takes years to build, by a lot of people and at the cost of a lot of resources so they will be placed only in strategic points and more important/critical points will get bigger ones. So caution on placing that big towers in the top of a big mountain in the middle of nowhere $\endgroup$
    – jean
    Commented May 4, 2018 at 12:52
  • $\begingroup$ @kingledion Even better! It's already way more castles than I want to think up lords for, so I'll make it an impoverished land with lots of haunted ruins. Boom, done. $\endgroup$ Commented May 4, 2018 at 15:48

This is a pretty complex question even if it seems simple. A couple things.

1. Castles can exist for many reasons

  • Military/defense/control
  • Fortress of a city
  • Resource protection
  • Geographic location

2. Castles range greatly in size and scope

  • From small wooden keeps to large stone keeps with curtain walls

3. Castles don't just pop up in geographically even distribution

  • Your map is going to play an important role in placement
  • Population density is important as well, it takes a lot of humans to build and maintain a fortress
  • The geopolitical climate, a bunch of nations that get along won't really be building castles.

So, to lead off, castles are expensive. Really expensive. You're not going to invest the resources into one unless absolutely necessary.

Before you can get a count you need to figure out your map. You need to know where rivers and roads (medieval transportation routes) are. Identify mountains and passes. Figure out your political boundaries and the history of the nations involved. Its easy for us to think of castles as all being contemporaries but in reality they were built over the course of millennia. Keep population density in mind as well.

Step 1: Establish geography, population, geopolitics and history

Once you complete that step (which is the biggest one) you can begin placing cities and forts. Where things intersect be it political boundaries/transportation routes/geographically important points, or better yet a combination of them, are good candidates for large defensive structures.

Step 2: Find overlapping/intersecting points of interest

Now you have sites for major defensive structures. Next step would be keeping in mind resources. Stone is hard to quarry with medieval technology, I also hear its heavy. This makes it expensive. As such, some places may not have stone defenses. Wood, sandstone, regular stone, even dirt can all be used to create fortifications.

Step 3: Figure out resources available for building

Once you get your big/major locations sorted out you can work your way down, the less complex and smaller the more common they will be. If you are talking about a small wooden keep you can have pretty much as many as you want.

So in short...we can't really give you a number. There are a lot of variables to consider.

Run through the process above and you should get to a decent answer, do what makes sense, don't just try to pick a certain number.

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    $\begingroup$ Point well made. I thought I would spare the forum this information for the sake of brevity, but I see that I was wrong to do that. Nevertheless, your answer will help me formalize and organize what I have so that I can either work to answer the question for myself or represent it to the forum in a better form. Thank you! $\endgroup$ Commented May 3, 2018 at 21:40
  • $\begingroup$ to further extend your point of military/defense/control you can look at the real world example of King Edward I and his conclusion to the Welsh wars where he built 8 castles specifically to ensure that the Welsh lands remain dominated $\endgroup$
    – BKlassen
    Commented May 3, 2018 at 21:41

As Dan Clarke says, your overall density is at least one castle per lord. The wealthier/more economically strategic a lord's holdings are, the more likely it is to be stone; the more powerful, wealthy and influential the lord, the more likely he is to have more than one castle (not necessarily all stone).

According to this Quora post, how many lords you have, as a percentage of the population, depends on your exact setting. For instance, militarized borders will have more lords (with better fortified castles), while some cultures had so many people who could claim some sort of title that most of them didn't have castles.


As a general rule of thumb, I'd suggest that cultures where political power has been consolidated by a few, 5% of your population will be lords with castles, up to 10% for militarized areas.

Given your time setting, here's what most of your castles are going to be like. Shad buries the lede, so you can skip to about 3 minutes in if you want. However, he does try to give you a good idea of the ratio of stone-castle-density to not-stone-castle-density.


  • $\begingroup$ @JBH Better? I realize it's still not great, but I'd like to come back and add more info when I can. $\endgroup$ Commented May 3, 2018 at 21:59
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    $\begingroup$ Much. More in-depth analysis would make it perfect, but much, much better. I've removed by downvote and upvoted. Cheers! $\endgroup$
    – JBH
    Commented May 3, 2018 at 22:18
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    $\begingroup$ "I'd suggest that cultures where political power has been consolidated by a few, 5% of your population will be lords with castles". 1 in 20 people being a castle owning lord seems very high to me. $\endgroup$ Commented May 4, 2018 at 10:30
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    $\begingroup$ 1 in 20 families, perhaps. And that would be the most minor of castles, some pointy sticks in the ground around a small stone building. $\endgroup$
    – MSalters
    Commented May 4, 2018 at 13:56
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    $\begingroup$ Even 1 in 20 families seems quite high. If you think about how many people work in a proto-typical castle, and then how many people live in the shadow/protection of said castle, I'd think it'd end up closer to 1 per 1,000 (for a small castle) or 1 per 10,000 (or more) people (for a big one). $\endgroup$
    – Doug
    Commented May 4, 2018 at 17:07

1 keep per Lord. These range from simple large stone houses that are defensible to large castles that can house hundreds and withstand an army. Poorer lords may only have thick wooden walls around their home, or may make large wooden forts instead of small stone keeps.

Along the border, especially on roads and rivers, and important harbours you might find a string of small stone or wood forts to keep enemies out, most will be fairly small and basic, acting more as a trip wire and a show of force against raiders. Depending on the financial situation of the kingdom these could be crumbling old forts that are ready to fall apart or well maintained structures that can have thriving trading towns surrounding them and soldiers in nice new shiny armour.


The number of lords and castles depends on a whole host of issues. Sometimes there will be many castles per lord, sometimes they'll be forced to have a single small keep or a palace. 1 Castle per lord, was used as a fairly reasonable means of keeping things simple, with the limited information we were given.

What is the population of the country?

The higher the population generally means more nobles to ensure no one noble gets too much power, and that they are able to maintain their lands. Bureaucracy wasn't as advanced back then, having too many people under one nobles control is simply too hard to handle. Also a king would not want a noble who rivals his power, they can't always prevent it, but eventually it reaches the point where a war occurs and either the noble is broken or the noble becomes the king.

How much power does the king have?

In countries where kings were dominate, generally castles were limited. In countries where nobles had more power, there were more castles.

Spain has 2500 castles because it had a very turbulent history. The Muslim invasion of Spain saw hundreds of keeps and castles built by both sides to defend their land. Then during the Reconquista, more castles were built. However after the Reconquista was completed, virtually no castles were built, there wasn't the need. Many castles fell into disrepair as the nobles and the royalty couldn't maintain all of them.

France before the 16th century had an extremely weak king. The nobles ruled and fought amongst each other while the kings generally stayed out of the way. They built lots of keeps and castles during those times to deal with their neighbours. After the rise of the absolute French monarch, new castles were not built by the nobles. Smaller keeps and forts were abandoned or taken over by the King, and some castles were destroyed, others were taken by the King and some were left to the nobles.

In England, after the Second English Civil War, the parliament ordered many of the castles and keeps damaged or destroyed to ensure any future civil war would be easier to put down. Again after this time new castles were not made, only palaces.

Japan in the Edo period, after Japan was united, made a law that only one castle could be built in a lords domain unless given special permission by the Emperor.

Now Bavaria was mentioned in another message, with 620 or so castles. Bavaria was frequently caught up in wars, and there was no strong central government. So the nobles, towns, cities and anyone with money really built keeps and castles to protect themselves.

So what type of government do you have?

Peaceful or Warlike?

A country at peace and having known peace for a long period of time will not have a lot of keeps and castles. Older keeps and castles will exist, but most won't be kept up.

If raiders aren't a problem, why would a mine have anything more than a basic stockade? That's money being wasted.

Nobles didn't often have a lot of money, building castles and keeps to show off is a waste that could be better spent on creature comforts, impressing allies with gifts and bribes, etc. A palace is much better for showing off than a castle.

If the border is a desert with very few people living in it, than castles aren't necessary for defence. Instead a few keeps on or near the oases will ensure no army can invade unnoticed, while saving money.

Now if war, either between nobles or outsiders is common, you're going to see lots of castles. Like in Bavaria, every place of some importance is going to have a castle, keep or fort. So is there lots of fighting or not?

Trade Routes?

Is the nation landlocked, an island, is it surrounded by equally powerful or more powerful nations right on the border, is it isolated forests, deserts or mountains, or is most of it coastline?

The major ports, rivers that are usable for shipping and major roads near the borders will have a castle or keep. The size of it, as well as the upkeep depends on how peaceful the neighbours are. Again more warlike neighbours will see well built castles, peaceful smaller nations will get keeps.

Population centers

Are people spread out all over the country or are they mostly centered in a few key areas?

If this is a desert kingdom with a few cities and towns around oases, ports or rivers, you'll need very few castles. If it's more like England with multiple cities, many large towns, and a whole host of villages, castles will be spread out to cover all the various areas.

That's about it, figure out those details and you can come up with the number of castles.

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    $\begingroup$ Regrettably, this does not answer the OP's question. It simply changes the variable from "castles" to "lords." So, what's a realistic number of lords per-capita? $\endgroup$
    – JBH
    Commented May 3, 2018 at 21:21
  • $\begingroup$ I'm not sure this is entirely accurate, 1 keep per Lord, I'm fairly certain I've read of close friends to kings having more than one keep in their name $\endgroup$
    – BKlassen
    Commented May 3, 2018 at 21:38

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