Hi, I'm Matthew 👋

I'm a Software Developer from New Zealand

Flatting - A Payment Model

5 minutes
July 31, 2011

I’ve been flatting in the same flat for six years now, some flatmates come and go and others stay the same. During this time, we have been trying to find a good model for figuring out how much to charge each flatmate.

We started with a basic model - everyone pays the same. This was all well and good as all of the rooms were a fairly similar size. Then we started to have issues with couples sharing rooms and what happens when you want to rent out that small room? Is a system where what people pay is simply based on intuition good enough?

I didn’t think it was - so I devised a new model. It still has it’s limitations but is fairly sound, seems to be fair, is not inordinately complex, and corresponds well with what would seem intuitively right.

The model centers around the concept that when you rent you are in effect paying for the space you use. In the model all space - be it your bedroom, the kitchen or the toilet is treated as equal. It’s the amount of space that an area uses that counts.

Lets give a simple example of the system at work. Andy, Bob, and Charlotte all live in a nice new house and all have the same sized bedrooms - one each! If the rent is $300, they will all end up paying $100 each - it’s fair! But why? The facts:

The model:

Seems simple enough right? Lets show a slightly more complicated example: The facts:

The model:

Hopefully that all made sense. Would you agree that this seems fair? The system does have some limitations, most of these can be resolved by adding a weighting to the value of each square m, but this adds an additional level of complexity.

Some of the limitations and other considerations are:

What do you think? What do you use for your own flat? Do you think this model is fair? Too complicated? Want to try it for yourself? I have included a spreadsheet for good measure - Rent Calculator