Splitting Rent Fairly When Roommates Have Different Room Sizes
A common fair approach weights each person's share of rent by their room's proportional size (and sometimes amenities like a private bathroom), rather than splitting the total evenly — the room with more square footage or more private amenities takes a proportionally larger share of the total rent.
An even split feels fair in theory but breaks down quickly once room sizes differ meaningfully, which is one of the most common sources of roommate friction over money.
A worked example
A $2,400 total rent, split between a 200 sq ft room and a 150 sq ft room (350 sq ft combined, excluding shared space): the larger room's proportional share is 200/350 ≈ 57%, or $1,371, while the smaller room's share is 150/350 ≈ 43%, or $1,029 — a meaningfully fairer split than a flat $1,200 each, which would overcharge the smaller room and undercharge the larger one relative to actual space received.
Accounting for a private bathroom or other amenities
Beyond raw square footage, a private bathroom, a walk-in closet, or a significantly better view are commonly assigned an additional flat premium on top of the size-based split — there's no single universal formula for this, since it depends on what the specific roommates agree an amenity is worth, but making the adjustment explicit avoids ongoing resentment over an unstated but real difference.
Keeping the agreement clear and documented
Whatever method is used, writing down the exact agreed split (and the reasoning behind it) avoids later disputes about whether the arrangement was ever actually fair — particularly useful if a roommate later moves rooms or a new roommate joins and needs to understand the existing arrangement.