Landlord Calculator

Operating Expense Ratio Calculator

See what share of a property's gross income goes to operating expenses alone, before the mortgage even enters the picture.

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Opens live in the Rental Flow app, no account needed.

What this calculator does

The operating expense ratio (OER) divides a property's annual operating expenses by its annual gross income. Unlike the break-even ratio, it deliberately excludes debt service, so it isolates how efficiently the property itself is run, separate from how it's financed.

The formula

Operating Expense Ratio = Annual Operating Expenses ÷ Annual Gross Income

Lower is better. It means more of every dollar collected survives expenses before financing is even considered. Use it to track expense management over time on one property, or compare operating efficiency across similar properties.

Worked example

$24,000 income, $8,400 expenses

Annual gross income	$24,000
Annual operating expenses	$8,400
Operating expense ratio	35.00%

At 35%, just over a third of gross income goes to keeping the property running, leaving the rest to cover debt service and, hopefully, cash flow.

What is a good operating expense ratio?

The operating expense ratio (OER) is annual operating expenses divided by gross income, shown as a percentage. For many residential rentals it lands somewhere between 35% and 55%, but it varies with property age, amenities, and who pays the utilities. A lower ratio means more of each rent dollar survives as income.

OER excludes the mortgage, so it isolates how efficiently the property runs. Track it over time: a creeping ratio can reveal rising maintenance, taxes, or management costs eating into your margin before they show up as a cash-flow problem.

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Frequently asked questions

What does the operating expense ratio measure?

OER measures what share of gross rental income is consumed by operating expenses, such as taxes, insurance, maintenance, and management, before any mortgage. A 45% ratio means 45 cents of every rent dollar goes to running the property and 55 cents is net operating income.

Does OER include the mortgage payment?

No. OER deliberately excludes principal and interest so it reflects how efficiently the property itself operates, independent of how it is financed. That makes it comparable across properties with different loans or none at all.

What expenses count in the operating expense ratio?

Operating expenses include property taxes, insurance, repairs and maintenance, property management, utilities you pay, and a vacancy allowance. They do not include the mortgage, depreciation, or capital improvements like a new roof, which are treated separately.

Is a lower operating expense ratio always better?

Generally a lower ratio means more income reaches your bottom line, but an unusually low number can mean deferred maintenance that will surface later. Compare the ratio to similar properties and make sure low expenses reflect efficiency, not neglect.