Stellaris Habitability and Colonization Guide

Habitability is the number that decides whether a new planet is a gift or a slow drain on your empire. Nail it and a size 20 world fills up with productive pops who barely cost you anything. Botch it and you're paying way more upkeep for way less output, wondering where your consumer goods income went. The system is pretty simple once you see the actual numbers, so here's how it works and how to use it when you're picking your next colony.

How Habitability Affects Pop Growth

The core rule is one sentence. Every point of habitability below 100% does two bad things: pops on that world pay 1% more upkeep and burn 1% more amenities, and their job output and growth speed both drop by 0.5%. Run that on a rough planet and it gets ugly fast. A 20% habitability world means +80% upkeep and −40% output and growth. At 0% you're looking at doubled upkeep and amenities use, plus half output and half growth. That's not a colony at that point, that's a charity you fund.

The starting number depends on how well the climate matches what your species evolved on. The nine regular habitable types sit in three groups: dry (Desert, Arid, Savanna), wet (Ocean, Continental, Tropical), and cold (Arctic, Alpine, Tundra).

| Match | Base habitability | | --- | --- | | Exact planet type match (Desert species on a Desert world) | 80% | | Same climate group (Desert species on Arid, both dry) | 60% | | Different climate group (Desert species on Ocean) | 20% | | Gaia World, Ecumenopolis, Ring World | 100% | | Tomb World, Machine World, Hive World | 0% | | Habitat, tier I / II / III | 40% / 50% / 60% |

Homeworlds add +30% for the species that came from them, which is why your capital always sits at 100% even though it's "just" an exact type match. Relic Worlds also come in at 80% for everyone, which is part of why they're such a good find.

The growth math

Pop growth on a planet follows a curve, not a straight line. The game tracks something called planet capacity, which comes from three places: unused housing, free district slots, and the pops themselves. Regular habitable worlds and Relic Worlds grant +4 capacity per open district slot. Gaia Worlds, ecumenopolis planets, Hive Worlds, and Ring Worlds give +6. Tomb Worlds, Machine Worlds, and habitats only give +3. So a fresh size 20 planet with nothing built on it has a ton of capacity, pops multiply quickly early on, and then the curve flattens as the world fills toward its ceiling. Total growth caps at 5.0 per planet no matter what.

Habitability multiplies your growth speed directly. A colony sitting at 60% grows 20% slower than the same colony at 100%, on top of every pop there producing less. Growth also slows empire-wide as your total population climbs, so wasted growth on bad worlds genuinely costs you later.

So who cares about 10% here or there? You should, because the penalty stacks three ways on one colony. Growth is slower, job output is lower, and upkeep is higher. And upkeep isn't just food. Biological pops pay consumer goods based on their living standards too, so a low habitability world quietly eats your consumer goods income while also producing less of them. It's a double hit.

The amenities death spiral

There's a second-order problem on top of the raw numbers. Low habitability pops use more amenities, and short amenities drag happiness down. Unhappy pops lower the planet's approval rating, which lowers stability, and low stability cuts resource output again. A 50% habitability colony that also runs an amenities deficit can end up producing close to half of what the tooltip says the jobs should give. Fix the habitability or fix the amenities, but don't ignore both.

Practical thresholds

The game color codes worlds for you, and the cutoffs are worth memorizing. Green means at least 70% for someone in your empire who can colonize. Yellow is 40% to 69%. Red is below 40% for everybody you've got. You'll also get a confirmation popup if you try to settle under 70%, which is the game's way of saying "you sure?"

Pops won't even automatically resettle to a world below 20% habitability, so a red-class colony stays half empty unless you shove pops onto it yourself.

Fixing the number

You've got a pile of options and they stack. Four mid-game society techs each give +5% habitability empire-wide: Atmospheric Filtering, Hostile Environment Adaptation, Foreign Soil Enrichment, and Eco-Integration Studies. The Adaptive trait gives +10%, Extremely Adaptive gives +20% (and costs a lot of trait points), and Robust gives +30% if you can engineer it in. Nonadaptive is −10%, so don't pick it unless the points are buying something better. Lithoids get +50% habitability everywhere, which is a huge part of that species' appeal.

Robotic pops have a 50% habitability floor instead. They never drop below half no matter how awful the world is, which makes robots and cyborgs the natural pioneers for Tomb Worlds and other rough real estate.

One warning: habitability above 100% does nothing. Once you've stacked techs and traits on a Gaia World, the extra points are wasted, so stop spending on it.

Scouting Colonizable Planets Early

Exploration is where colonization actually starts. When any owned ship enters a system, habitable planets show up along with their world type, but that's all you get. The details only appear after a science ship surveys the system: planet size, available districts, planetary features, blockers, modifiers, and the exact habitability for every species in your empire. Until then the planet icon shows blue, which just means "habitable, go look."

Get a second science ship building early, and a third not long after. The auto-survey mode already chases systems with habitable planets first, then works outward from your capital, so it's a decent fallback if you don't want to micromanage. Manual control is better in the first decade though, because you want your ships pushing toward chokepoints and circling your borders while they hunt for real estate.

What makes a planet worth taking

Size comes first. Habitable planets run from size 12 to 25, and moons from 10 to 15. Size is your district slot count, and districts are jobs and housing, so a size 22 beats a size 13 almost every time even at slightly worse habitability.

Then check the planetary features. That's what limits your mining, generator, and agriculture districts, and each climate group leans a different way: wet worlds carry more agriculture features, dry worlds more generator features, cold worlds more mining features. If your empire is starving, a Continental world with big farming deposits is worth more than a prettier Desert one. Count blockers too, since every blocked tile is a district slot you're paying to unlock.

Two things stop a colonization cold. A planet with an unresearched anomaly can't be settled, and neither can one hosting a pre-FTL civilization. The anomaly one bites people regularly, so if you've got your eye on a world, get a scientist on that anomaly now rather than when the colony ship arrives.

Keep an eye out for the special stuff

Surveys also surface the rare finds. Gaia Worlds are perfect for every species and usually carry nice modifiers. Relic Worlds sit at 80% for everyone, come with research-boosting features, and can be restored into an ecumenopolis later without the usual prep work. Tomb Worlds look terrible at 0% base but often hide events or free trait rolls, and some of them are great terraforming targets. And watch for barren rocks with the Terraforming Candidate modifier. They're worthless now, but they're free planets later once you have the right tech.

Surveys also reveal the orbital deposits in a system, which feels pointless in 2205 and matters a lot once you start building habitats. More on that below.

Terraforming and Climate Restoration Options

Terraforming is how you turn a 60% world into an 80% world, or a useless rock into a colony. The first tech is Terrestrial Sculpting, and the costs scale with how far you're bending the planet.

| Change | Cost | Time | Tech | | --- | --- | --- | --- | | Same climate group (e.g. Arid to Desert) | 2,000 energy | 5 years | Terrestrial Sculpting | | Different climate group (e.g. Arid to Ocean) | 5,000 energy | 10 years | Terrestrial Sculpting | | Tomb, Machine, or Hive World to regular | 10,000 energy | 20 years | Climate Restoration | | Barren world with Terraforming Candidate (matching type) | 5,000 energy | 10 years | Climate Restoration | | Barren world, cross-category flip | 15,000 energy | 20 years | Climate Restoration | | Regular world to Gaia | 7,500 energy | 10 years | World Shaper perk |

The World Shaper ascension perk also cuts all terraforming costs by 25%, so the real Gaia price is closer to 5,625 energy. That's a bargain for what you get: 100% habitability for every species, +10% happiness, +10% resources from jobs, +15% pop growth speed, and a big +50% pull for automatic resettlement. Gaia Worlds tend to roll positive modifiers too.

Climate Restoration is the sleeper tech. It fixes Tomb Worlds, sure, but it also unlocks every barren world flagged as a Terraforming Candidate, and those are everywhere once you start looking. A few thousand energy for a whole extra planet is one of the best deals in the game.

Making it faster (and slower)

The Terraforming Gases edict speeds terraforming up by 50%, which turns a 10-year job into less than 7. On the flip side, running an exotic gases deficit slows you down by 20% at the minor level and up to 80% at catastrophic. If you're terraforming seriously, keep your gas income healthy or buy the stuff.

The Ecological Adaptation tech lets you terraform planets you've already settled. Pops on the world take a −20% happiness hit while the work is ongoing, so it's usually fine but not free. Mostly you'll use this to fix a big colony's climate in place instead of abandoning it.

The fine print

Terraforming strips planet modifiers. Bleak, Lush, Irradiated, Hazardous Weather, Hostile Fauna, Wild Storms, all of it goes away when the planet is converted. So terraforming a Lush world with +10% food output actually makes it worse for farming, at least habitability-wise it gets better. Check the modifiers before you commit, because sometimes the planet you've got is already the right one.

Gene modding instead

The other path is changing your pops instead of your planets. The Glandular Acclimation tech lets you rewrite a species' climate preference, and from then on every world of that new type reads 80% instead of 20%. One terraform fixes one planet. One gene mod fixes every planet of that climate you own or will ever take. For a wide empire sitting on six cold worlds, modding your main species to Arctic preference beats paying for six separate conversions.

The trade-off is time and flexibility. Glandular Acclimation is a deeper tech tree than Terrestrial Sculpting, and applying a template takes a special project. It's also species-wide, so think about whether you actually want everyone adapted or just a settler sub-species. Robots have it easy here: machine pops swap habitability traits with no tech gate at all.

Habitats and Ecumenopolis Alternatives

Sometimes the answer isn't a better planet, it's not using planets at all. Habitats and city worlds both sidestep the climate question, and a mature empire usually wants some of each.

Habitats

Once you have the Orbital Habitats tech, a construction ship can build one over a star or planet. It takes 5 years, 200 influence, and 1,500 alloys with a mechanical shipset (750 alloys plus 2,625 food for biological shipsets). One habitat per system, and they can't go above moons or into systems that already have a ring world. Colonizing one is faster than a planet, since the colony develops at double speed.

The catch is that a habitat's size depends entirely on the system it's in. You get 0.25 max districts per planet or star in the system, multiplied by your habitat tier: 0.25 at tier I, 0.5 at tier II, 0.75 at tier III. A system with eight celestial bodies gives 2 districts at tier I and 6 at tier III. A system with two bodies gives you almost nothing. So build habitats where it's crowded.

Resource districts work the same way. Reactor districts, astro-mining bays, and research districts are each limited by the matching deposits in the system, at 1 plus half the deposit value. This is why you scout deposits carefully. A system loaded with minerals and research deposits is a habitat goldmine even if every planet in it is a barren rock.

Habitability runs 40%, 50%, and 60% across the three tiers, which is the real weakness. Upgrading the capital building (Habitat Administration to Central Control to System Control) needs 1,000 pops for tier II and 2,500 for tier III, plus the Habitat Expansion and Advanced Space Habitation techs. The Void Dwellers origin gets 1.5x the jobs from habitat districts and can build housing buildings on them, which is why that origin plays so differently. Everyone else mostly uses habitats for research, mining, trade, and industry, and accepts that pops there will want for amenities.

Ecumenopolis worlds

An ecumenopolis is a planet entirely wrapped in city, and it's the best alloy and consumer goods engine a biological empire can build. Getting there takes the Arcology Project ascension perk (non-gestalt empires only) plus Anti-Gravity Engineering tech. Then you run the decision on a qualifying planet: every district must be a city or industrial district, all blockers cleared, 20,000 minerals and 200 influence down, and 10 years of waiting.

The payoff is big. Perfect 100% habitability for all species, +20% resources from jobs, +15% pop assembly speed, +15% monthly organic pop growth, and +50% automatic resettlement pull. Arcology districts pack far more housing and jobs than regular city districts, and a fully built ecumenopolis holds a staggering number of pops.

The limitation is what it can't do. No farming districts, no mining districts, no generator districts. A city world makes alloys, consumer goods, unity, and research, and imports literally everything else. So don't convert your breadbasket. Convert a world that's already wall-to-wall industry.

If you found a Relic World while scouting, you get a shortcut. The Restore Ecumenopolis decision costs the same 20,000 minerals and 200 influence and takes the same 10 years, but there's no need to fill the planet with city districts first, and the Former Relic World feature keeps giving +10% research from jobs afterward. It's strictly less work for a better result.

Ring Worlds are the endgame version of the same idea: perfect habitability, enormous segments, and the only place to get certain district combos. Between restoring ruined ones and building your own, that's a late-game project, but it's the logical finish line for this whole tech path.

Prioritizing Which Planets to Settle First

You can't colonize everything at once, so order matters. A colony ship runs most organic empires 200 alloys, 200 food, and 200 consumer goods (lithoids pay minerals instead of food, machine empires pay energy), takes a year to build, and doesn't actually consume any pops. Landing starts a development period of about 2 years and 10 months during which the colony is defenseless and produces nothing. The finished colony comes with a tier 1 capital and 100 pops of whatever species you loaded.

Speed that up where you can. The Expansion tradition tree gives +25% colony development speed, the AI-Controlled Colony Ships tech gives +50%, and a councilor with Frontier Spirit helps too. Piling those on turns a three-year wait into roughly a year and a half, which is a real difference when you're racing a neighbor to a system.

The actual priority order

First, high habitability and big. A size 20+ world at 70% or better near your borders is a no-brainer, take it immediately. Second, worlds with the resource features you're short on. Third, anything inside or near a chokepoint system you need to hold. Fourth, low habitability worlds, and only once you have a plan for them, whether that's terraforming, gene modding, or settling them with robots.

Influence is usually the real constraint, not minerals. Outpost starbases and colony-ready claims all pull from the same pool. If you're choosing between a fourth colony and claiming the chokepoint that protects your other three, take the chokepoint.

Don't ignore empire size entirely. Every district adds 0.5 empire size, and a new colony starts racking those up fast. That's not a reason to skip colonizing, the pops and jobs are worth far more than the size penalty, but it is a reason not to grab a size 13 red-class world in 2210 just because it's there. Garbage planets keep.

Use every species you've got

Here's the trick that unlocks the map. The game only cares about the species doing the colonizing, and a colony ship lets you pick which species rides it. So a migration treaty with a desert-dwelling neighbor turns all your 20% Arid worlds into 80% Arid worlds, because their pops can settle them. Conquest, uplifting pre-sapients, and the slave market all do the same thing. A xenophile empire with three or four climate preferences in the pool basically has no bad planets left.

Check the species rights, though. Only species with Colonization Allowed can be loaded onto colony ships, and if you flip that right off mid-flight, the ship won't be able to land.

A quick worked example

Say it's 2210 and you've surveyed three candidates. One is a size 22 Savanna at 60% with big mining features, twelve systems out. One is a size 14 Continental at 80% right next door. One is a size 19 Arctic at 20% with a Terraforming Candidate barren moon in the same system.

Take the size 22 first. The extra nine district slots and the mining deposits outweigh the habitability gap, and you can terraform it to your home climate later for 2,000 energy since Savanna to your type is probably a same-group flip. Take the size 14 second, cheap and quick, and let it grow while you save influence. Leave the Arctic alone for now, but keep the system, because that barren moon plus Climate Restoration means two colonies for the price of one later.

And that's the whole habitability question in one decision: a size 22 at 60% that you fix in ten years almost always beats a size 14 at 80% that stays small forever. Bigger stage first, climate second.