Split a bill when someone moves in or out.

Worked example

A 120.00 bill covers 1 to 30 September 2026, so each day costs 4.00. Alex and Sam live there all 30 days. Jo moves in on 16 September and is there for 15 days. Days 1 to 15 have two people (2.00 each); days 16 to 30 have three (about 1.33 each). Alex pays 50.00, Sam 50.00 and Jo 20.00, which add up to 120.00.

How it works

Each day costs bill / days in the period, split among the people there that day. A person is counted as there on both their move-in date and their last day. If nobody is home on some days, that cost is shared by person-days. Totals are rounded to the cent so they add up to the bill. This is different from simply weighting by days present, because a day with fewer people costs each of them more.

Sources and basis (checked 2026-10-08): arithmetic on the numbers you enter, with no external constants or published figures. Amounts are in whatever currency you enter. This is a calculation aid, not legal, tax or financial advice.

FAQ

How do I split a bill when a roommate moves out mid-month?

Enter the dates the bill covers and the roommate last day. Each day is split only among the people there that day, so the roommate who left pays only for the days they were home.

Is this the same as splitting by days present?

No. Splitting the whole bill by total days present gives a similar result, but a daily split charges each day only to the people there that day, which matches how the cost actually accrued.

Does the move-out date count as a day there?

Yes. The move-in date and the last day there are both counted. Enter the day after if you want to exclude the day they left.

What if nobody is home on some days?

The cost of those days is spread over everyone by their person-days, and the result tells you how many days that was.

Can I use it for rent or internet as well as utilities?

Yes. Any shared bill that covers a date range works, including internet, a streaming plan or a month of rent.