How to split rent and bills with roommates

Pick the split method before you pick the numbers

Most shared households use one of three approaches, and the argument usually isn't about which is fairest in theory — it's that nobody agreed on one at all before the first bill arrived.

• Equal split. Everyone pays the same share of everything. Simplest, and correct when the rooms and usage are genuinely comparable.
• Room-adjusted split. The person with the bigger room, the en-suite, or the private balcony pays a larger share of rent specifically — while groceries and utilities usually still split equally, since square footage doesn't change how much electricity someone uses.
• Usage-based split. For the bills where usage genuinely differs — a household streaming service one roommate never uses, or a parking spot only one car needs.

Decide this once, out loud, before the first bill — not after someone's already annoyed about it.

How to actually price an uneven room

"The big room pays more" is easy to agree on and impossible to act on, because nobody knows how much more. Here are two methods that produce a number instead of a negotiation.

By floor area

Measure the bedrooms and split rent by their share of the total bedroom space. Shared space — kitchen, living room, bathroom — is not counted, because everyone uses it equally.

A €1,500 flat with bedrooms of 20m², 14m² and 11m² has 45m² of bedroom space. That is 44%, 31% and 25%, so €667, €467 and €366. It takes one tape measure and ends the discussion permanently.

By what each room would rent for

Floor area ignores things people actually pay for: the en-suite, the balcony, the room facing the street at 6am, the box room with no window. If the rooms differ in more than size, price them the way a listing would — then normalise to the real rent.

Say you judge the rooms at €700, €550 and €400 individually. That totals €1,650 against actual rent of €1,500, so each pays their room's share of that total: 42%, 33% and 24% — €636, €500 and €364.

Whichever method you use, write the resulting percentages down somewhere both of you can see. In kisir, rent is then an expense split by exact amounts, or by shares if the ratio is simple, and the numbers stop being re-litigated every month.

Agree on the list, not just the number

Write down what's actually shared: rent, utilities, internet, household supplies, maybe a cleaner. Then write down what isn't: someone's personal streaming subscriptions, their own groceries if you don't share a kitchen budget, a guest's meal. The argument almost never comes from bad math — it comes from two people having a different list in their head.

The category that causes the most trouble is household consumables — washing-up liquid, bin bags, toilet roll, salt. Individually trivial, collectively noticeable, and almost always bought by the same one person. Either put them on the shared list properly, or accept that whoever keeps buying them is subsidising the flat.

Log it when it happens, not at the end of the month

Whoever pays a shared bill enters it the same day, for the people it actually covers — not automatically split three ways if only two of you use the parking spot. In kisir, one person creates the group and shares a six-character code or link; everyone else joins with a name, no account needed, and logs expenses as they happen. A roommate without a smartphone can still be added by hand and appears in every split.

Utilities that move with the season

Heating in February is not heating in July, and a flat where one person moved in during the summer will produce an argument in the winter.

Two things worth deciding in advance:

• Split each bill as it arrives, not an averaged monthly figure. Averaging feels tidier, but it means whoever moves out in spring has paid for a winter they were only half present for. Real bills, split when they land, are always defensible.
• Handle estimated readings honestly. If a bill is estimated and a later one corrects it, split the corrected bill when it arrives rather than going back and editing a month everyone has already settled. The correction evens out on its own, and the settled month stays trustworthy.

Where one person genuinely drives a cost — a space heater in one bedroom all winter, a home office running all day — that is a usage-based conversation to have once, not a monthly grievance.

The deposit is not rent

The deposit is the single most disputed number in shared housing, because it is paid once, sits untouched for a year or more, and comes back changed.

Record it as an expense at move-in, against whoever actually paid it and for the people it covers. It is common for one person to front the whole deposit — that person is owed that money by the others from day one, and if it is not in the ledger, it is only in their memory.

At move-out the landlord returns some or all of it, usually to one person's account. That person now owes everyone else their share — record those as payments between you, so each one clears against the deposit each person put in at the start. If deductions are made, be specific about cause: damage to one person's room is theirs, a professional clean of the whole flat is shared. "We'll sort the deposit later" is the single most expensive sentence in a shared lease.

Handle the cases that break an equal split

Every shared household eventually hits one of these:

• Someone moves out mid-lease. Split what happened while they were there normally; stop including them in anything after. Don't try to average it retroactively — that's where "who owes who" turns into a spreadsheet nobody trusts.
• One bill, two people paid it. The deposit split half on one card, half on another. Record both payers on the same expense rather than pretending one person covered it and squaring up separately.
• A bill only some of you use. Streaming, a parking spot, a gym in the building — split it only among the people it's actually for, not the whole household by default.

Someone moves out and someone moves in

A replacement roommate is not the same person as the one who left, and treating them as one continuous slot is how debts get inherited by people who never agreed to them.

Settle up completely with the person leaving before the new person's first expense. That means: net the balances, make the transfers, and record them. The outgoing roommate leaves at zero. Everything after that date belongs to the new household.

The deposit usually needs its own conversation, because the landlord will not return it until the end of the lease. The common arrangement is that the incoming roommate pays the outgoing one their deposit share directly on the handover — record that as a payment so the ledger shows the deposit obligation moving across.

Guests, partners and the person who is always there

This one is genuinely awkward, and worth agreeing on before it happens rather than after four months of somebody's partner using the hot water.

A guest for a weekend is noise; nobody should be logging it. A partner who effectively lives there is a fourth person in a three-person flat, and it shows up in utilities and consumables rather than rent.

Two honest options: agree a flat monthly contribution to bills, or add them to the household properly for the things they actually use. What does not work is saying nothing for a year and then raising it during an argument about something else.

Settle monthly, not per bill

Don't reimburse every grocery run individually — net the month off first, then make the fewest transfers that clear it. Three roommates and a month of bills usually resolves to one or two payments, not eight.

Pick a date and keep it — the day after rent leaves, or the first Sunday. A settlement that happens on a schedule is a routine; one that happens when somebody finally gets annoyed is a confrontation.

When a payment is made, record it, so the group can see the debt cleared. An unrecorded transfer is how the same person gets asked for the same money twice.

Keep the record past the lease

Deposits and final utility bills get disputed weeks after everyone's moved out. Export the ledger to CSV or Excel before anyone leaves — free, any time, in kisir — so "I think I paid for that" has an actual answer instead of three people's different memories.

The final bills usually arrive after the last person has moved out, which is exactly when the group has stopped paying attention. Keep the group going until the closing meter reading and the deposit are both settled. In kisir, the group closes itself once every balance is zero, and anything added after that asks before re-opening — so a flat nobody lives in doesn't quietly collect new costs.