Your place
What each room is worth to each person
For each person, split the rent across the rooms the way they'd happily pay. Put more on the room they want. The numbers are a wish, not a promise, so it's fine if they don't add up exactly.
How Divvy picks the rents
When rooms aren't the same, splitting the rent in equal parts isn't fair, and haggling over a number nobody can justify is how housemates fall out. Divvy asks everyone the one question that matters: what is each room worth to you? From those answers it does two things.
First it gives each person the room that makes the group happiest overall, so the rooms go where they're wanted most. Then it sets each room's rent so that nobody would rather have paid someone else's rent for their room. That's the test of a fair split: if you can look at what everyone else pays and still be glad of your own deal, no one can say they were hard done by. The rents always add up to the real total.
Fair-division researchers call a split like that "envy-free", and that it can always be done is a known result (Svensson 1983; Alkan, Demange and Gale 1991). The site Spliddit brought it to the public. Divvy works it out with the Hungarian algorithm and checks its own answer before showing it.
It's a guide to a fair starting point, not a tenancy agreement. Nothing you type leaves your device.