I'd recommend going with something like medieval Italy. Here's a map showing the different states that occupied the peninsula: click here
And, according to Wikipedia:
Area
• Total: 301,338 km2 (116,347 sq mi)
Wingshaw
I am having problems trying to decide how big to make an area I am mapping. I am looking to have 11 (human) kingdoms on a large peninsula. But I have no idea the area I should have each kingdom take. I am looking for them to all border or be at least close to at least one other kingdom with some unclaimed while lands. I know there are several factors such as terrain but I am just looking for some averages or some guidance on how to decide how big of an area.
I'd recommend going with something like medieval Italy. Here's a map showing the different states that occupied the peninsula: click here
And, according to Wikipedia:
Area
• Total: 301,338 km2 (116,347 sq mi)
Wingshaw
Formerly TheHoarseWhisperer
It is partially dependent upon the age, the viable sizes of countries ebbs and flows through history. Look at Italy (which seems apropos), went from small tribes to kingdoms to Rome back to city states then eventually to a unified Italy. In the medieval period through the Renaissance there were more than 11 kingdom/separate-political-entities on the peninsula. For smaller size in Israel you can go way back to the time of the Canaanites where Abraham waged war on behalf of 4 Kings against another 5, which who knows how much area the occupied it could have been, relatively small like the areas around modern Israel and Lebanon and some of Syria and Jordon, or their kingdoms could have extended in area all the way to the Euphrates. Also remember that while these were kings they were often allies or vassals of bigger players.
In short the extent of a Kingdom is limited by the ability to gather military power, to project that power, and the ability to organize the country. All of which are affected by terrain, culture, and general level of education.
It can be as small as you want. It is a form of government, it is not related to a specific size.
It usually came as something prestigious to be a kingdom but some large countries never had the title of kingdom: Grand Duchy of Lithuania or the Archduchy of Austria.
On Earth some kingdoms are only a few hundred square kilometres. The smallest ever (probably) according to the BBC https://en.wikipedia.org/wiki/Kingdom_of_Tavolara
is only 5 sq km
My Deviantart: https://vincent--l.deviantart.com/
A good rule of thumb is that a kingdom will encompass one or two levels of administrative districts and economically dominate those districts. Each of those districts will likely be not much more than a few days travel in size from the seat of its local government and not much more than a week from the king's seat. The size of a kingdom will therefore vary widely, because travel distance is affected enormously by things like mountains, swamps, deserts, rivers, and population.
As Azelor points out, some kingdoms will be simple administrative districts where the ruler has delusions of grandeur (or a controlling position on critical infrastructure like the only passable spot in a mountain chain for hundreds of miles).
Take a look at the Holy Roman Empire (which was not holy, roman, or an empire): https://upload.wikimedia.org/wikiped...er_Staufer.svg Too many little things to count one the appendages of two hands and the Wikipedia page has a lovely little animation that shows how the silliness evolved.
To start, +1 for thinking about how big the area you are covering is before you start making the map. Far to few people do that. Knowing the latitude is also important.
You really need to work out more details like what is the setting for? If you are telling a story, you need an appropriate size for that story. If it's for a game, it needs the right area for that game. What's around the area being mapped? Neighbours, what's across the water and how far, etc. What's the climate? What are the technology and social structure like? What's the history? You don't need fine detail, but a rough idea of things like that will give you an idea of the extent you need.