Guide Utility billing math

RUBS calculation: the formula, step by step

By MeterEase · Updated October 13, 2026

RUBS formula: unit share = (unit factor ÷ building total of that factor) × bill. For a 50/50 blend, share = 0.5 × (unit sq ft ÷ total sq ft) + 0.5 × (unit occupants ÷ total occupants). Round each share to the cent so the shares add up to the bill exactly.

The calculation in five steps

Start with the master bill total for the period.
Take out any common-area amount the lease says the owner pays.
Add up the factor for every unit: total square footage, total occupants, or both.
Divide each unit’s factor by the total, and blend the percentages if the lease uses a blend.
Multiply by the bill, round to the cent, and make sure the shares add back to the bill.

Worked example: a fourplex with one vacant unit

Example numbers only. The water and sewer bill is $412.60. The lease uses a 50/50 blend of square footage and occupants. Unit 4 is vacant; it stays in the totals at its usual 2 occupants and the owner pays its share, so the other tenants are not billed for an empty unit.

Unit	Sq ft	Occupants	Sq ft share	Occupant share	Blended	Amount
1	800	2	22.22%	25.00%	23.61%	$97.42
2	800	1	22.22%	12.50%	17.36%	$71.63
3	1,000	3	27.78%	37.50%	32.64%	$134.67
4 (vacant)	1,000	2	27.78%	25.00%	26.39%	$108.88, paid by owner
Total	3,600	8	100%	100%	100%	$412.60

Unit 1, written out: 0.5 × (800 ÷ 3,600) + 0.5 × (2 ÷ 8) = 0.5 × 22.22% + 0.5 × 25.00% = 23.61%, and 23.61% × $412.60 = $97.42. Tenants are billed $303.72 in total and the owner pays $108.88.

Same bill, different methods

Method	Unit 1	Unit 2	Unit 3	Owner (Unit 4)
Square footage	$91.69	$91.69	$114.61	$114.61
Occupants	$103.15	$51.58	$154.72	$103.15
50/50 blend	$97.42	$71.63	$134.67	$108.88

Run your own units in the free RUBS calculator, which uses the same vacancy rule and rounding.

Rounding so the shares match the bill

Percentages rarely land on whole cents. Round each share to the cent, then add any leftover cent to one unit so the billed shares plus the owner’s share equal the bill. Never round in a way that bills tenants more than the building was charged.

Before the first RUBS bill

Allocation rules, fee limits and disclosure rules differ by state and city. Some places restrict RUBS for certain utilities. See what to check before you bill.

Run this split every month without the spreadsheet

MeterEase reads the master bill PDF, applies your method and vacancy rule, and emails each tenant their share with the source bill attached, after you check the numbers. Plans start at $14/month.

Questions

What is the RUBS formula?

Each unit’s share equals its allocation factor divided by the total of that factor for the building, multiplied by the bill being split. For a 50/50 blend, calculate the square footage share and the occupant share, then average them.

How do you calculate RUBS with a vacant unit?

One common rule keeps the vacant unit in the totals, so its share is calculated like any other unit and the owner pays it. Occupied units then pay the same amount they would if the unit were rented. The lease should say which rule you use.

Do the RUBS shares have to add up to the bill?

Yes. Billed shares plus any owner-paid share should equal the bill being split, so tenants are not charged more than the utility charged the building. Round to the cent and put any rounding cent on one unit.

Should common-area use be taken out first?

Many landlords deduct a set percentage or amount for common areas such as irrigation, a laundry room or a house meter before splitting, and the owner pays it. If you do, state the deduction in the lease.

Can I add an admin fee to a RUBS bill?

Some places allow a disclosed admin fee and some cap or prohibit it. Check the rules where your property is, and show any fee as its own line. This is general information, not legal advice.

Related guides

Sources

Example numbers on this page are made up to show the math. This guide is general information, not legal advice; rules differ by state, city and utility.