Utility bill split calculator
Enter this month's electricity, gas, water and internet bills, list your roommates, and see exactly what each person owes. Split every bill equally, by the days each roommate was actually home, or by how much each person uses. No account needed.
How do you split utility bills with roommates?
Split each bill by the rule that fits it, not the whole pile at once. Internet and water are usually shared per head, because the cost barely moves with who is home. Electricity and gas track real consumption, so they are fairer split by the days each roommate was present, or by a usage weight when one person clearly uses more. This calculator applies a rule per bill, adds up each roommate's shares, and keeps the totals matching the bills to the cent.
How do you split an electric bill with roommates?
Take the amount printed on the electricity bill and divide it by each roommate's weight for that month. If everyone was home the whole month and nobody runs anything unusual, that is a plain even split. If someone travelled for two weeks, count days present instead, and their share drops in proportion. If one roommate runs an air conditioner, a space heater or a gaming rig, give them a usage weight above 1.0 and everyone else pays less.
Try it: enter this month's utility bills
Pre-filled with an example month. Edit any field to calculate your own.
Used as the baseline for the days-present split. Change it to 28 or 31 to match the billing period.
Each roommate pays in proportion to the days they were in the home this month.
Bills
Tick the checkbox on any bill that should be shared per head no matter which mode is selected. Internet starts ticked.
Roommates
Days counts how long each person was in the home this month. Usage is a weight: 1.0 is an average user, 1.5 pays half again as much, 0.5 pays half.
How this split utilities calculator works
Every bill is split by one formula: each roommate's weight is their usage weight multiplied by their days present, divided by the days in the month. Equal mode pins both factors at neutral, so every weight is 1. By days present pins usage at 1 and lets the days do the work. By usage pins days at the full month and lets the usage weight do the work. A bill you tick as always equal ignores the mode entirely and is shared per head, which is what internet, and often water, should be.
Each bill is then divided in whole cents by largest remainder rounding. Everyone gets the floor of their exact share first, and the leftover cents go to the largest fractional parts, with ties going to the roommate listed first. That means a bill of $100.00 between three people comes out as $33.34, $33.33 and $33.33, never $33.33 three times with a cent missing. Each person's month total is the sum of their per bill shares, so the grand total always matches the bills exactly.
If a bill ends up with no weight at all, for example a days-present split in a month where nobody entered any days, the calculator falls back to an equal split and says so next to that bill rather than leaving it unallocated. Everything runs in your browser. Nothing you type is sent anywhere or stored.
Worked example: three roommates, one 30 day month
Ana and Ben were home all 30 days. Cleo was away for the second half of the month, so she was present 15 days. The household picked By days present, and ticked internet as always equal because the line costs the same whoever is home.
| Bill | Amount | Ana (30 days) | Ben (30 days) | Cleo (15 days) |
|---|---|---|---|---|
| Electricity | $142.80 | $57.12 | $57.12 | $28.56 |
| Water | $48.00 | $19.20 | $19.20 | $9.60 |
| Internet (always equal) | $59.99 | $20.00 | $20.00 | $19.99 |
| Month total | $250.79 | $96.32 | $96.32 | $58.15 |
Cleo's weight is 15 divided by 30, so 0.5, against 1.0 each for Ana and Ben. The three weights add up to 2.5, which is why Cleo pays a fifth of the electricity and water while Ana and Ben pay two fifths each. Internet is the exception: it is shared per head, and the two leftover cents on $59.99 go to the two largest fractional shares, so Ana and Ben pay $20.00 and Cleo pays $19.99. The three month totals add up to $250.79, the exact sum of the three bills.
Common questions
How do you split utility bills when a roommate is away half the month?
Switch the calculator to By days present and enter the days each person was actually living in the home. A roommate who was there 15 days of a 30 day month carries half the weight of someone who was there the whole month, so their share of electricity, gas and water drops to match. Bills you have marked as split equally, like internet, stay even for everyone.
Should internet be split per person or by usage?
Per person. An internet line costs the same whether one roommate streams all evening or nobody is home, so there is no usage to measure and no fair way to meter it. That is why the internet row is set to split equally by default here, and you can tick the same box on any other bill that should be shared per head instead of per unit used.
One roommate runs the air conditioning all summer. How should we split the electric bill?
Use the By usage mode and give that roommate a higher usage weight. A weight of 1.5 means they pay one and a half times what a roommate on 1.0 pays, and 2.0 means double. Agree the number together before the bill arrives, and apply it only to the bills it affects, usually electricity or gas, while internet and water stay equal.
Do the shares always add up to the exact bill?
Yes. Each bill is divided in whole cents using largest remainder rounding, so any leftover cent goes to the largest fractional share first, and ties go to the roommate listed first. The per person amounts always total the exact bill, and each person's grand total is the sum of their per bill shares.
Is this utility bill split calculator free to use?
Yes, and no account is needed. The whole calculation runs in your browser, so the amounts you type never leave the page. If you want the same split applied every month, with the bills logged as they arrive and a running balance per roommate, that is what the Faiyr app is built for.
More free calculators
Utilities come back every month
This calculator handles one month. Faiyr logs each bill as it arrives, keeps the split you agreed on, and shows a running balance per roommate so nobody has to redo the math in January and again in February.