Whether your empire in Stellaris consists of a few heavily-developed planets or hundreds of star systems, it will become more difficult to manage as it grows. Empire Size, otherwise known as Sprawl, represents the challenges of managing a galactic civilization by imposing penalties the larger an empire becomes.Related: Stellaris: How Does Space Combat Work?

Nobody is immune to Sprawl penalties, but with careful planning and management you can anticipate its effects. Knowing how your Empire Size will affect your income - and how it won't - will help you make better choices throughout any Stellaris campaign.

How Is Empire Size Calculated?

To determine your Empire Size, the game simply adds up all the contributing factors. Colonies are the largest individual sources of Sprawl, but factors such as population and the number of systems within your borders add up quickly to increase Empire Size as well.

Empire Size Factors

What Does Empire Size Do?

Early in the game you won't need to worry about Empire Size at all. As long as it's one hundred or less, it has no effect. For every point of Sprawl above a hundred, however, the cost of Technologies increases by one tenth of a percent and the cost of Traditions increases by one fifth of a percent.

These numbers are pretty small, but don't be fooled - they add up. Let's say you're at exactly one hundred Empire Size and you annex a system with a habitable world to colonize. After several years you've built three districts and there are six pops on your fledgling colony. This relatively minor expansion just increased your tech costs by two percent for the rest of the game, in addition to any other increases from population growth on other planets or further expansion you did in the meantime.

Additionally, there are several costs and penalties that are calculated directly from Empire Size. This means that the larger you grow, the more harder it will be to keep ahead of certain risks. Use the following chart to see how Empire Size will impact you:

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How To Reduce Empire Size

There are several ways to reduce the amount of Sprawl your empire generates. Adopting the right ethics, government types, and traits will cause specific Empire Size factors to count less. For example, if your empire has the Fanatic Pacifist ethos, pops will generate thirty percent less Sprawl, effectively increasing your Empire Size by only 0.7 points each. Be on the lookout for Traditions, Civics, and even Technologies that will help keep Sprawl under control.

Having skilled Governors in all your Sectors is a great way to reduce your Empire Size rating. Pops in a Governor's Sector generate two percent less Sprawl per Governor level. In a highly-populated Sector, that's a big reduction.

Empire Size modifiers are applied immediately to all present and future factors that they affect. This means that unlocking a new modifier will have an immediate impact on your Technology and Tradition costs.

Enhancing a planet's specialization by giving it an Ascension Tier can also reduce your overall Sprawl. Each Ascension Tier assigned to a planet reduces its Sprawl by five percent. This is an expensive undertaking best saved for the mid- and late-game, but Ascending a populous, highly-specialized planet can help get your costs under control.

Anticipating Empire Size Gains

Since you can calculate how much your planned growth will affect your Empire Size, and by extension your costs, you can soften the blow by increasing your Research and Unity production. Staying ahead of the rising costs will allow you to maintain or even speed up your progress in these areas.

Pacifists might not be the most exciting ethos to play, but combined with Materialism or Spiritualism they can get a major advantage in Technologies or Traditions. The Pacifist ethos reduces the impact of Sprawl on your costs, while Materialism and Spiritualism increase your empire's Research and Unity production, respectively.

Next: Stellaris: How Do Planetary Invasions Work?