One roommate spends two weeks at their parents' place, or travels for work. The bills keep coming. Do they pay a full share of everything? Usually that feels wrong to everyone, including them.
Here is a simple way to handle it without a long group chat.
Sort bills into two piles
Fixed bills cost the same whether anyone is home or not. Internet is the classic one. Rent, if you split it by room, belongs here too. Split these equally (or by room, as you already do). Someone being away doesn't make the router cheaper.
Variable bills go up and down with use. Electricity, water and gas are the usual ones. These are the ones to split by days at home.
Split variable bills by days at home
- Count the days each person was home during the billing period.
- Add them up. This is the total of "person-days".
- Divide the bill by the person-days to get a price per day.
- Multiply by each person's days.
Pick a rule for "home" before you start. A common one: if you slept there, it counts. Write it down once and stop debating.
Worked example (illustrative numbers)
Three roommates, a 30-day month. Ana and Ben are home all month. Cam is home for 15 days.
- Internet: $60 (fixed)
- Electricity: $120 (variable)
- Water: $45 (variable)
Internet, equal split: $20 each.
Electricity, by days. Person-days: 30 + 30 + 15 = 75. $120 / 75 = $1.60 per day. Ana pays $48, Ben pays $48, Cam pays $24.
Water, by days. $45 / 75 = $0.60 per day. Ana pays $18, Ben pays $18, Cam pays $9.
| Internet | Electricity | Water | Total | |
|---|---|---|---|---|
| Ana | $20 | $48 | $18 | $86 |
| Ben | $20 | $48 | $18 | $86 |
| Cam | $20 | $24 | $9 | $53 |
The three totals add up to $225, which is exactly the three bills combined. These numbers are made up; swap in your own.
A caveat on electricity
A fridge runs whether Cam is home or not. If that bothers you, split a small slice of the electricity bill equally and the rest by days. Say, a quarter equal and three quarters by days. Any ratio works as long as everyone agrees before the bill arrives.
Do the math faster
The utility bill splitter takes a bill and each person's days at home and gives you the shares. Free, no signup.
FAQ
Does a roommate who is away still pay rent? Usually yes. Rent covers the room whether or not you're in it. The days-at-home split is mainly for usage bills.
What if the away roommate used the place for just a few days? Same method. Three days at home means three person-days in the count.
Do we have to be this exact? No. Some flats just round to half a share. The point is to agree on a rule early so nobody has to ask for a favour.
Keep track without the nagging
Billmates is a web app, still on the waitlist, that tracks who owes what in a shared home. It never holds or moves your money. You pay each other the way you already do. Roommates join from a browser link. No ads. If you'd like to hear when it's ready, leave your email below.