Split Evenly
The most basic way to split the bill is by splitting it evenly. If there are two people living in an apartment, they'll both have to pay 50% regardless of the amount of space they're using. If you're living conditions are completely split into two, splitting the rent 50-50 is the best idea.
Split By Space
If you have a big apartment or house and space is rented unevenly, asking the person using lesser space for 50% isn't really justified. So, if you are using two rooms while your roommate is using one, it's ethical to pay 66% and ask your roommate for 33%.
Split by Income
If you're living with a really close friend or with a spouse and still want to split the rent, it's a great idea to split by income. It helps both of us get through things together without putting too much financial pressure on one individual.
