Square footage
Split rent by bedroom size, see each room's share of the private bedroom area, and copy a clear formula-based explanation for roommates.
One common way to calculate this is to divide each bedroom's square footage by the total private bedroom square footage, then multiply that share by the total rent.
Formula: room rent = total rent x room square footage / total private bedroom square footage.
This keeps the default method narrow and explainable. Shared living rooms, kitchens, bathrooms, hallways, and utilities are not counted unless your group agrees to use a separate common-space rule.
A square-footage split is useful when bedrooms are clearly different sizes and room size is the main difference roommates want to count.
If one room also has a private bath, parking, much better storage, more privacy, more noise, or an awkward layout, keep those assumptions visible as separate premiums or discounts instead of hiding them in the square-footage number.
The method assumes private bedroom area is the best starting point for dividing rent between rooms. It does not say that the result is the only fair answer.
If two people share one bedroom, the room-size split can still handle the bedroom portion. You can enable common spaces if part of the rent should also reflect how many people use shared areas.
Usually the square-footage method starts with private bedroom area only. Shared areas can be handled separately if the group wants part of the rent to follow people in each room.
A larger room will pay more under this formula because it owns a larger share of the private bedroom area. You can still adjust the result if the group agrees that another feature should matter too.
It is a clear starting point, not a final authority. Square footage works best when room size is the main difference and other features are minor or handled as visible adjustments.
Count them only if your group agrees they are part of the private room value. Another option is to leave the bedroom measurement simple and add a visible premium or discount.
Share the total rent, each bedroom size, the formula, and any adjustments. The copied explanation is meant to make the assumptions easy to review without sounding like a demand.