Planet Capacity
Planet Capacity (colony) in the Stellaris encyclopedia: Planet Capacity is determined by Housing and additional space from undeveloped Districts, which varies with the habitability of the Planet. Clearing Blockers can further increase capacity.
Planet Capacity in the game's words
The encyclopedia entry as the game shows it in its tooltips; underlined words open their own entry or page here.
Planet Capacity is determined by 
Housing and additional space from undeveloped 
Districts, which varies with the habitability of the Planet. Clearing 
Blockers can further increase capacity.
Biological Pops grow fastest at mid-capacity, benefiting from growth bonuses, but face penalties as the 
Colony nears its limit.
Entries that mention Planet Capacity
More in Colony
Source: common/game_concepts (concept_planet_capacity) and localisation/english, Stellaris Cygnus v4.5.2 (9776).