# Split utilities calculator: fixed charges plus usage

Canonical URL: https://www.evenoutapp.com/tools/utilities-split-by-usage-calculator
Updated: 2026-10-06

Take the fixed charges off the bill and split them equally among the people in the split. Split what is left in proportion to each person's usage, then add the two shares. For a $96 bill with $24 fixed and nights home of 30, 30, 15 and 5, the shares are $33.00, $33.00, $19.50 and $10.50.

Key points:
- Fixed charges split equally among the people counted. The rest of the bill splits by each person's usage.
- Usage can be kWh, gallons, nights home, days since move-in or room size, as long as everyone uses the same unit.
- A usage of 0 leaves the person out entirely, including the fixed charges.
- Shares are rounded to the cent and add up to the bill exactly.

## When to split a bill by usage

Split by usage when the bill grows with use and the people on it use very different amounts. A roommate who is home 5 nights a month and one who is home 30 nights do not use the same amount of water. When everyone is home about the same, an equal split is simpler, and [how to split utilities](https://www.evenoutapp.com/guides/how-to-split-utilities) compares the methods using one bill.

Many bills have two parts, and this calculator splits them differently. A water bill can carry a fixed monthly fee plus a charge for each unit of water used. The fixed part is owed whether the tap runs or not, so it splits equally. Only the part that depends on use is split by use.

## How the calculator works

It splits the fixed charges equally among everyone whose usage is above 0, splits the rest of the bill in proportion to usage, and adds the two shares for each person.

1. Enter the total bill and the fixed charges (0 if the bill has none).
2. Enter each person's usage in one unit. For electricity, kilowatt-hours from a plug-in energy monitor work, where one kWh is 1 kilowatt (1,000 watts) used for 1 hour. For water, gallons or nights at home work. Days since move-in suits someone who arrived mid-month, and room size suits a cost tied to space (the same idea as the rent calculator that uses room size).
3. Leave unused slots at 0. A person at 0 is not in the split, so they pay nothing and are not counted for the fixed charges.
4. Read each person's share. The shares add up to the bill to the cent.

## Worked example: a $96 water bill

Say four roommates get a $96 water bill. It lists $24 of fixed charges (a service fee and a sewer base charge), so $72 depends on use. They agree to measure use in nights at home, which came to 30, 30, 15 and 5, or 80 nights in all.

The $24 of fixed charges splits four ways: $24 ÷ 4 = $6.00 each. The $72 splits by nights: $72 × 30 ÷ 80 = $27.00, $72 × 15 ÷ 80 = $13.50 and $72 × 5 ÷ 80 = $4.50.

| Person | Nights home | Usage share | Pays, with $6.00 fixed |
|---|---|---|---|
| Person 1 | 30 | $27.00 | $33.00 |
| Person 2 | 30 | $27.00 | $33.00 |
| Person 3 | 15 | $13.50 | $19.50 |
| Person 4 | 5 | $4.50 | $10.50 |

Splitting all $96 by nights would give $36.00, $36.00, $18.00 and $6.00. The person home 5 nights would pay $4.50 less, while the utility still bills the $24 of fixed charges whoever is home. An equal split would give $24.00 each.

## Enter the result in EvenOut

To record the bill in EvenOut, add it as an expense and open the split picker. "Exact amounts" takes $33.00, $33.00, $19.50 and $10.50, and the pill reads "All assigned" once the four add up to $96. "Shares" gives the same result with 22, 22, 13 and 7, because 64 shares of a $96 bill is $1.50 a share, and each person's dollar share shows under their name. EvenOut splits are cent-accurate, so leftover cents are shared out rather than lost.

## Common mistakes

- **Using 0 for someone who is on the lease but away.** A 0 removes the person from the split, fixed charges included. If they should still share the fixed charges, give them a small usage above 0 that the group agrees on.
- **Leaving the fixed charges at 0 when the bill lists them.** The flat fees then follow usage, and the person who uses least pays less than an equal share of charges that do not depend on use.
- **Measuring one person differently.** Everyone needs a number in the same unit for the same billing period.

## Where to go next

Electric and gas bills mix fixed and usage lines in their own way, which [how to split electric and gas bills](https://www.evenoutapp.com/guides/split-electric-and-gas-bills) walks through. When one meter serves several homes, see [how to split utilities in a duplex](https://www.evenoutapp.com/guides/split-utilities-in-a-duplex), and the glossary has an entry on [what a water submeter is](https://www.evenoutapp.com/glossary/water-submeter). The water version, by who is home, is in [how to split a water bill](https://www.evenoutapp.com/guides/split-water-bill). Everything on shared bills is collected under [subscriptions and bills](https://www.evenoutapp.com/topics/subscriptions-and-bills).

## Frequently asked questions

### How do I tell a fixed charge from a usage charge on my bill?

A fixed charge is a line that stays the same however much is used, such as a monthly service fee or a base charge. A usage charge grows with the amount used, such as a price per kWh or per gallon. If a line is unclear, compare two bills where the usage was different. A line that stayed the same is fixed.

### Can I mix units, such as kWh for one person and nights for another?

No. The calculator compares each number with everyone's numbers added together, so mixed units give shares that mean nothing. If only one person has a measured reading, such as a heater on a plug-in monitor, multiply those kWh by the price per kWh on the bill (when it has one flat price), charge that person for it directly, and enter what is left as the total.

### Does the unit I pick change the answer?

No. Only the proportions matter. Nights of 30, 30, 15 and 5 give exactly the same shares as 60, 60, 30 and 10, so you can use kWh, gallons, nights or days, as long as every person's number is in the same unit.

## Sources

- [U.S. EPA: Setting Small Drinking Water System Rates for a Sustainable Future](https://www.epa.gov/system/files/documents/2022-06/FINAL%20Sustainable%20Water%20Rate%20STEP%20Guide_508.pdf)
- [U.S. EIA: Glossary, kilowatthour](https://www.eia.gov/tools/glossary/index.php?id=Kilowatthour)