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One figure per person, every month. Rent and the four household utilities go in as separate amounts, each is divided on the basis that fits it, and the shares are added up into a monthly total per person — plus what the same arrangement costs over twelve months. Rent is shared per room, electricity follows the units each person used, water and gas follow how many people live in each room, and internet is shared equally.
The most anyone owes each month (Room 1)
Room 1 $944.44 · Room 2 $921.03 · Room 3 $901.53 — $2,767.00 a month across 5 bills.
One row per room. People in this room drives the water and gas lines — put 2 in a room a couple shares. Electricity units drives the electricity line; leave it blank and that bill falls back to an equal split.
Each bill is divided and rounded on its own, so its shares add back up to that bill exactly, and only then are the shares totalled per person.
Three views of the same flat: the monthly total against the yearly one, the electricity rate, and the rounding step on the internet bill.
The table above prints the answer; this one prints the sum that produces it. Same flat, same five bills, same three rooms — every line here can be checked against the bill in your hand and the meter reading.
| Line | Bill | Divided on | Room 1 | Room 2 | Room 3 |
|---|---|---|---|---|---|
| Rent | 2,400.00 | per room, three rooms | 800.002,400.00 ÷ 3 | 800.002,400.00 ÷ 3 | 800.002,400.00 ÷ 3 |
| Electricity | 156.00 | by units, 380 / 260 / 160 of 800 | 74.10380 × 0.195 | 50.70260 × 0.195 | 31.20160 × 0.195 |
| Water | 72.00 | by headcount, 1 / 1 / 1 | 24.0072.00 ÷ 3 | 24.0072.00 ÷ 3 | 24.0072.00 ÷ 3 |
| Gas | 54.00 | by headcount, 1 / 1 / 1 | 18.0054.00 ÷ 3 | 18.0054.00 ÷ 3 | 18.0054.00 ÷ 3 |
| Internet | 85.00 | equally, three rooms | 28.3485.00 ÷ 3, + leftover cent | 28.3385.00 ÷ 3 | 28.3385.00 ÷ 3 |
| Each room pays | 2,767.00 | five lines added down | 944.44800.00+74.10+24.00+18.00+28.34 | 921.03800.00+50.70+24.00+18.00+28.33 | 901.53800.00+31.20+24.00+18.00+28.33 |
| Over 12 months | 33,204.00 | the monthly figure, twelve times | 11,333.28944.44 × 12 | 11,052.36921.03 × 12 | 10,818.36901.53 × 12 |
Round every share down to the cent first, then hand the leftover cents to the shares with the largest fractional parts. On this page each of the five bills is divided on its own basis and rounded on its own, so the shares of each bill add back up to that bill exactly; only then are the five shares added across the rooms and multiplied by twelve.
One line does not come out even. 85.00 of internet split three ways is 28.3333… each. Three shares rounded down to 28.33 total 84.99 — a cent short of the bill. The leftover cent goes to the share with the largest fractional part, and all three fractions are 0.3333, a tie, so it goes to Room 1: 28.34 / 28.33 / 28.33, which adds back to 85.00 exactly. Every other line divides evenly — rent 2,400.00 ÷ 3, water 72.00 ÷ 3, gas 54.00 ÷ 3, and electricity 156.00 ÷ 800 = 0.195 a unit across 380 / 260 / 160 units — so the only rounding on the whole page is that one cent on internet, and the room totals of 944.44 / 921.03 / 901.53 and the yearly 11,333.28 / 11,052.36 / 10,818.36 all balance to the cent.
Two of those rows are worth a second look. Electricity is the only line with a rate in it: 156.00 across 800 units is 0.195 a unit, and that rate is the number to check against the bill, because it is the same for every room and it is what the provider is actually charging. Internet is the only line where the division does not come out even — a third of 85.00 is 28.333333, so the three shares are rounded down to 28.33 first and the cent left over goes to the share with the largest remainder, which is why Room 1 reads 28.34 and the other two read 28.33. Three identical figures would add to 84.99 and the column would be a cent short of the bill.
The last row is the one that matters when a bill changes. A rent rise, a new internet tier or a guest staying for a month each land as a different number in one cell of this table, and the room totals move by exactly that much — which is the whole reason for writing the arithmetic out instead of carrying a running total in someone's head.
A restaurant bill is settled once and then it is over. A household bill comes back next month, and the month after that, so whatever rule you pick in the first month is the rule you are still living with in the twelfth. The arithmetic does not change at all — the difference is that the rule has to survive repetition, and a rule that has to be re-argued every month is not a rule yet.
That is why this page puts the whole month in one place instead of answering one bill at a time. Rent, water, gas and internet are flat: they are the same figure whether anybody is home or not, so the fair thing to do with them is fix the basis once and stop discussing it. Electricity is the one line that moves, so it is the one line that should follow something measurable — the units on the meter, or an agreed weight if there is no sub-meter.
Two numbers come out of the same table. The household number — 2,767.00 a month in the example above — is what the flat costs to run, and it is the figure to keep an eye on when a bill jumps. The per-person number is what each person transfers, and it is the only one that has to be exact, because a share that is a cent out is a share somebody will notice.
When the split is written down line by line, every person can see which line makes them the largest payer. In the example, Person 1 pays the most and the reason is one row: 74.10 of a 156.00 electricity bill, because 380 of the 800 units were theirs. Nobody has to be told that the arrangement is fair — the row says it. That is the whole argument for putting the arithmetic in a table rather than describing it in a sentence, and it is the part that stops the monthly conversation from starting over.
Write down which lines are flat and which one moves, what the moving line follows, and what happens when the flat's total changes. A rent rise, a new internet tier or a month with a guest all land in the same table as a different number in one cell, so the arrangement does not have to be renegotiated to absorb them. Nothing on this page decides any of that — it only does the division and keeps the five lines straight.
Anything that arrives on a repeating monthly cycle and is shared by the people living there: the rent, electricity, water, gas and the internet line. The test is the repetition, not the amount — a one-off cleaning fee or a key deposit belongs to move-in day, not to the monthly table, and putting it in the monthly column would make every month look more expensive than it is. Add it to the first month by hand if you want the first month to match a bank statement.
It belongs in the same table but not on the same basis. Rent is charged for the space, so it is divided per room; water and gas follow how many people are actually living in each room, which is a different question from how big the room is. Keeping them as separate lines in one table is what lets a two-person room pay more for water while still paying one room's rent — merge them into a single figure and that distinction disappears.
Because of one line. Rent, water, gas and internet are identical for all three rooms, so the only row that separates them is electricity: 74.10 against 50.70 and 31.20. The gap between the largest and smallest monthly total is 42.91, and the whole of it comes from the meter. If Person 1's units came down to match Person 3's, the three totals would move to within a couple of cents of each other without anything else changing.
Put 2 in the People in this room box for that room and leave the others at 1. Water and gas then divide four ways instead of three, so the shared room carries two shares of those lines, while rent still divides per room and the couple's room still pays one room's rent. If the flat has agreed the couple should carry a bigger share of the space as well, that is a rent question rather than a utility one — the split rent calculator covers rent by room size and by income.
Change only the line that actually moved. Rent, internet and the fixed part of the water and gas bills are owed whether or not anyone is in the building, so they stay as they are; electricity is the line that follows the meter, so a month away shows up there as fewer units. That is the practical advantage of metering one line: a quiet month changes one cell instead of reopening the whole arrangement.
Because the monthly number is the smaller of the two, and the yearly one is what the arrangement actually commits you to. A 944.44 monthly share is 11,333.28 over twelve months, and that is the number to compare against a different flat, a different room or a different basis. It is not a projection — the table assumes the same five bills every month — so treat it as "what this arrangement costs if nothing changes", not as a forecast.
No. The utility split calculator takes a set of utility bills and lets you choose a basis for each one separately, which is what you want when the flat is still deciding how to divide things. This page starts one step later: it fixes the bases, adds rent into the same table, and answers the monthly question — what does each person transfer, and what does that come to over a year. Use the utility page to agree the rule, then this one to see the monthly figure.
Because a share of a cent is not a whole cent. 85.00 split three ways is 28.3333 each, and three of those rounded down leaves a cent behind. This page rounds each share down and then gives the leftover cents to the shares with the largest fractional parts, so each line's shares add back up to that line exactly and the household column lands on the total. That is why the three internet shares read 28.34, 28.33 and 28.33 rather than three identical figures.