While the population of a colony or empire can not be determined exactly (for a variety of reasons, not just the fact there aren't really any real people in them), it CAN be guessed to a degree. Please note that the rates below were both determined by data on populations in the real world modern Earth as well as a LOT of guessing at how those rates may grow as Earth advances and obviously what we might say is the population of, say, a City could be off a little bit from what it really would be if your city really existed.
|COLONY SIZE TYPE||POPULATION|
|Base||10 - 50|
|Outpost||40 - 300|
|Village||300 - 1,000|
|Town||4,000 - 50,000|
|City||1,000,000 - 10,000,000|
|Utopia||15,000,000 - 45,000,000|
Your Empire: How Big IS It?
To determine the population of your settlement, first figure out what type of colony it is. (Look HERE for the standards) Now that you have your colony type determined, look above and find it; let's say for this guide you're looking for the population of a Town. Next to Town it says "4,000 - 50,000", this means your town will likely have a minimum of around 4,000 people and a maximum of around 50,000 people, you can go a little bit above the maximum or below the minimum, but not too much.
Now that we know the limits of what your Town's population can be, let's figure out the population. Look at your town, is it very big? Small? Does it have a lot of resources or only a few? Is the environment nice to live in, such as a forest or plains, in or is it harsh, such as a desert or the arctic? What sort of environments do your people thrive in and do poorly in? Let's say your Town is medium sized, has and abundance of resources, and is in a forest area by the coast (which your people love and thrive in).
So, with that said, your town will probably be able to support a lot of people, so let's say you have... 46,000 people living in your town. But wait, isn't that number a little weird? In fact, it is.There is no city in the world with such a flat number as say 1,000 or 46,000, they all have 1,112 or 47,426 or so on. So, to keep things realistic, let's say your town's population is actually 46,281.
Now that you know your Town's population, you can figure out the population of all your other settlements; to figure out the population of your empire*, just add together the populations of your settlements!
Those OTHER Citizens
Because this is a space based project and the various empires are bound to interact and some may even have more than one native sentient race, it is entirely up to you how to split your population between different races, just make sure that if you mention someone elses race they approve of the possibility of some of their citizens moving to your empire and that you aren't taking a species who dies in the cold and moving them to an outpost in an ice and snow covered tundra... Killng immigrants isn't exactly good for tourism or population growth...
*NOTE: Because a planet can be a HUGE place, there might be people not living in your major settelments there, so there could be, say, hundreds of people living in the forests of a continent on your homeworld on the opposite side of the world from or just far away from your capital(s). Please make reasonable adjustments to account for this when totally empire, system, and planetary populations.