How the ratio utility billing formula works
Tenant share = (unit factor ÷ building total of that factor) × master bill. The factor is square footage, occupants, bedrooms or an equal count per unit. A hybrid formula averages two factors.
Worked example: square footage with a vacant unit
A $180.40 water bill covers three units totalling 2,400 sq ft. Unit 1B (800 sq ft) is vacant, so the owner absorbs its share.
| Unit | Sq ft | Calculation | Share |
|---|---|---|---|
| 1A | 720 | 720 ÷ 2,400 × $180.40 | $54.12 |
| 2A | 880 | 880 ÷ 2,400 × $180.40 | $66.15 |
| 1B (vacant) | 800 | 800 ÷ 2,400 × $180.40 | $60.13, owner absorbs |
Choosing a method
- Square footage: common for heating, cooling and gas, which scale with space.
- Occupants: common for water and sewer, which scale with people.
- Bedrooms: a stand-in for occupants when you do not track headcount.
- Hybrid: blends space and people, often used for water in mixed unit sizes.
- Equal per unit: simple, often used for trash.
For more on how ratio utility billing works, see What is RUBS?
Questions
How do you calculate RUBS?
Divide each unit’s factor by the building total, then multiply by the master bill. For square footage, a 720 sq ft unit in a 2,400 sq ft building pays 720 ÷ 2,400 = 30% of the bill. Hybrid formulas average two factors, such as 50% square footage and 50% occupants.
Which RUBS method is the fairest?
It depends on what drives use. Water and sewer track people, so occupant count or a square footage and occupant hybrid is common. Trash is often split equally per unit. Gas and electric heating track space, so square footage is common. Use the method your lease states.
What happens to a vacant unit’s share?
In this calculator a vacant unit stays in the split and the owner absorbs its share, so occupied tenants do not pay for empty units. Its share is shown but not billed.
Is this calculator legal advice?
No. It does the arithmetic only. Rules on billing tenants for utilities vary by state, city and utility type, and your lease must allow it. Check local law before you bill.