Vacancy Rate for Rental Property: How to Estimate It and Why It Matters

What Is Vacancy Rate?

Vacancy rate is the percentage of time a rental unit sits empty and earns no rent over a given period, usually a year. It is one of the most overlooked inputs in rental analysis because a currently occupied unit makes vacancy feel like a non-issue.

Every property experiences vacancy eventually. Tenants move out, units need turnover work, and re-leasing takes time. Building a vacancy allowance into your projection keeps the analysis honest instead of assuming 100% occupancy forever.

How to Calculate Vacancy Rate

Divide the number of vacant days in a period by the total number of days the unit was available to rent, then multiply by 100. A unit empty for 18 days in a year has a vacancy rate of about 5%.

In a cash flow projection, vacancy is applied as a deduction from potential rent. If annual potential rent is $24,000 and you assume 5% vacancy, you subtract $1,200 to get $22,800 in effective rental income.

How to Pick a Realistic Vacancy Assumption

• Start with local data: census figures, property management reports, and rental market surveys for your city.
• A 5% to 8% vacancy allowance is a common starting point for stable long-term rentals, but markets vary widely.
• Higher turnover markets, student areas, or soft rental markets justify a larger allowance.
• Factor in typical turnover time in your area, since re-leasing can take weeks even in strong markets.
• When unsure, use a more conservative number so a bad month does not break the deal.

Worked Example

A single-family rental has potential annual rent of $30,000. The investor assumes a 6% vacancy rate based on the local market, which deducts $1,800 and leaves $28,200 in effective rental income.

That $1,800 difference flows straight through to NOI and cash flow. Skipping the vacancy allowance would overstate annual cash flow by $1,800 and inflate cap rate and cash-on-cash return, making a marginal deal look better than it is.

Vacancy Rate and Your Cash Flow

Because vacancy sits near the top of the income statement, small changes have an outsized effect on the bottom line. Raising a vacancy assumption from 5% to 10% can turn thin positive cash flow negative.

Treat vacancy as a stress-test lever. Run your base case, then re-run with a higher vacancy rate in a cash flow calculator to see whether the property still works when a unit sits empty longer than hoped.

Frequently Asked Questions