How splitting by square footage works
Shares are proportional to private space. Your share equals your bedroom's area divided by the total bedroom area, multiplied by rent. The common convention is to exclude shared spaces — the kitchen, living room, and any shared bathrooms — because everyone uses them equally. Measuring only private bedrooms keeps the math honest.
Worked example
Three roommates, $3,000 rent. Bedrooms measure 150, 120, and 90 sq ft — 360 sq ft in total.
- 150 sq ft room: 150 / 360 × $3,000 = $1,250
- 120 sq ft room: 120 / 360 × $3,000 = $1,000
- 90 sq ft room: 90 / 360 × $3,000 = $750
The three shares add up to $3,000 exactly. The calculator above uses the same formula and nudges trailing cents so totals always match rent to the penny.
When room size alone isn't fair
Square footage is objective, which is why it's popular, but it misses real value differences between rooms. A small bedroom with its own private bathroom can easily be worth more than a large one that shares. A big room with no window can be worth less than a smaller one with great light. If any of that applies, use the room-quality method on the main rent split calculator — it starts from an even split and layers percentage adjustments (private bathroom +15%, no window −10%, and so on) on top.
If incomes vary a lot between roommates, room size may not be the right axis at all. See split rent by income for a proportional-earnings approach. Moving in or out mid-month? The prorated rent calculator handles the partial month cleanly.
Measuring rooms accurately
Measure wall-to-wall along the two longest interior walls and multiply. Ignore built-in furniture footprints and door swings — you're pricing the room, not the usable floor. Use the same unit for every room; the sq ft / m² toggle only changes labels, since the underlying math is a ratio.
FAQ
Should common areas count?
No. Kitchens, living rooms, and shared bathrooms are used by everyone equally, so they're already priced into the base rent. Only measure private bedrooms when splitting by square footage.
What if we don't know exact square footage?
Pace the rooms off or grab dimensions from the floor plan or listing. Only the ratio between rooms matters — if every measurement is a little high or low in the same way, the split comes out identical.
Is splitting rent by room size legally required?
No. Roommates can agree to any split that everyone accepts — equal, by room size, by income, or a mix. Room-size splitting is a common convention, not a legal rule.