Guides

Fixed charges, empty days and rounding

Updated 2026-10-20

Three details decide whether a split survives a second look: which part of the bill is fixed, what happens to days nobody lived there, and where the odd cent goes.

Fixed charges

Many bills have a part that does not change with use. In UK energy bills it is called a standing charge, which Octopus Energy describes as "a fixed daily fee that gets added to your energy bill, regardless of how much gas or electricity you use". Internet plans, connection fees and service fees work the same way. Usage, by contrast, is priced per unit; Octopus's bill explainer shows the unit rate as what you pay for every kWh.

RoomProrate lets you enter the fixed part separately and splits it equally among the people you tick for that bill. It pre-ticks the people who lived there during that bill's dates and asks you to confirm. Typical agreements:

• Everyone on the lease shares the fixed part of every bill, even in months they were away.
• Only the people living there during the bill share it.
• The fixed part follows the same days as usage. In that case, leave fixed charges blank and add them to usage instead.

When you change someone's dates or add or remove a person, every affected bill asks for the confirmation again. This stops a person who moved out in March from being quietly added to the fixed charges of May.

Days when nobody lived there

With the daily split, the usage cost of an empty day has nobody to share it. RoomProrate shows it as Unassigned: vacant days instead of moving it onto someone. The check line still proves the total: people plus unassigned equals the bill. The household then decides who covers it. With person-days, empty days are spread over everyone automatically, which the results also explain.

Rounding without losing a cent

Money is paid in whole cents, but shares are rarely whole. Rounding every share up overcharges: 100,000 won split three ways and rounded up is 33,334 each, which collects 100,002. Rounding every share down leaves money unpaid.

RoomProrate does the arithmetic with exact fractions and rounds once, at the end, using the largest remainder method:

1. Each person gets the whole cents of their exact share.
2. The cents left over are handed out one at a time, starting with the largest dropped fraction.
3. Ties go in a fixed internal order, and the unassigned line is last in that order.

Currencies without minor units, such as Japanese yen and Korean won, are rounded to whole units. Amounts are never converted between currencies.

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