Vacancy rate is the single number that tells you how much of your rental property's income potential is sitting empty. A property with ten units and one unit vacant for a month has a vacancy rate that looks small on paper, but over a year those empty months add up to thousands of dollars in lost rent. This calculator takes your total units, the period you are measuring, and the number of unit-months that sat empty, then returns your vacancy percentage, occupancy rate, and the actual dollar amount you lost to vacancy.
Whether you own a small fourplex or manage a hundred-unit apartment building, the math is the same: divide vacant unit-months by total available unit-months, multiply by one hundred, and you get your vacancy rate. Pair that with your average rent and the calculator also shows how much money left on the table.
How to Use
- Enter the Number of Units — the total count of rentable units in your property. For a duplex this is 2; for a 12-unit apartment building it is 12. Include every unit you could reasonably rent out, even if some are off-line for renovations.
- Set the Period Length in months. Use 12 for a full calendar year, 6 for a half-year review, or 3 for a quarterly snapshot. The period length must be greater than zero.
- Input Vacant Unit-Months — the total number of months across all units that sat empty during the period. For example, if you have 12 units and each was vacant for roughly one month during the year, your vacant unit-months is 12. If two units were each vacant for three months, that is 6.
- Add your Average Monthly Rent per unit. This field is optional, but without it the calculator can only show percentages — you will not see the dollar loss. If rents vary widely across units, use a weighted average based on rentable square footage or simply the typical market rent.
The result card breaks down your total available unit-months, your vacancy rate (the headline number), the inverse occupancy rate, and the dollar impact: potential gross rent, lost rent from vacancy, and the actual gross rent you collected.
The Vacancy Rate Formula
The formula used by property managers, lenders, and appraisers is straightforward:
Vacancy Rate = (Vacant Unit-Months ÷ Total Unit-Months) × 100
Where:
- Total Unit-Months = Number of Units × Period Length in Months.
- Vacant Unit-Months = The sum of months each unit sat empty during the period.
For example, a 12-unit building measured over 12 months has 144 total unit-months (12 × 12). If that building had 12 unit-months of vacancy during the year, the vacancy rate is 12 ÷ 144 × 100 = 8.33%. The occupancy rate is the complement: 100% − 8.33% = 91.67%.
To translate that percentage into dollars, multiply vacant unit-months by your average monthly rent. With average rent of $1,000 per unit per month, the same building loses 12 × $1,000 = $12,000 in rent over the year. That figure — not the percentage — is what hits your bottom line and your net operating income.
What Counts as a "Good" Vacancy Rate?
Vacancy rates vary dramatically by market, property type, and season. As a rough benchmark:
- 0%–2%: Tight landlord market. Occupancy is essentially full, which is great for cash flow but can indicate you are pricing below market.
- 3%–5%: Healthy for most US multifamily markets. This range absorbs normal turnover between tenants.
- 6%–10%: Average or slightly soft. You may need to review rent pricing, unit condition, or tenant screening.
- 11%–20%: Soft market or property-specific issues. High turnover, deferred maintenance, or above-market rent could be the cause.
- Over 20%: Distress. Either the local market is extremely weak or the property has serious competition or condition problems.
National apartment vacancy rates in the US typically hover between 5% and 7%, according to Census Bureau data. Class A properties in strong job markets can run below 3%, while older Class B and C properties in tertiary markets often run above 8%.
Examples
Example 1 — A 12-unit apartment building. An investor owns a 12-unit building and measures the past 12 months. Across all units, there were 12 total vacant unit-months (roughly one month of turnover per unit). Average rent is $1,000 per month. The calculator shows a total of 144 unit-months, a vacancy rate of 8.33%, an occupancy rate of 91.67%, potential gross rent of $144,000, lost rent of $12,000, and actual gross rent collected of $132,000. That $12,000 vacancy loss flows straight into the operating expense section of the income statement.
Example 2 — A fourplex with high turnover. A small fourplex owner uses the calculator over a 12-month period. Two units turned over twice each, with one month of vacancy per turnover, plus one unit sat empty for two months waiting for a tenant. Total vacant unit-months is 6. With average rent of $1,500 per month and 48 total unit-months (4 × 12), the vacancy rate is 12.5%, lost rent is $9,000, and actual gross rent collected is $63,000 out of a potential $72,000. The 12.5% rate signals a tenant-retention problem worth investigating.
Example 3 — A 100-unit apartment community. A mid-sized property with 100 units over 12 months has 1,200 total unit-months. Leasing reports show 60 vacant unit-months. With average monthly rent of $1,800, the vacancy rate is 5.00%, lost rent is $108,000, and actual gross rent collected is $2,052,000 out of a potential $2,160,000. A 5% vacancy rate in a 100-unit building still represents a six-figure annual loss — which is why professional property managers aggressively chase occupancy.
How Vacancy Affects Your Investment Returns
Vacancy rate is not just an operational metric — it directly shapes the numbers lenders and buyers care about. Net operating income (NOI) equals effective gross income minus operating expenses, and effective gross income starts with potential gross rent minus vacancy and credit losses. A property that projects $200,000 in potential rent but carries a 10% vacancy allowance starts at $180,000 in effective income. Over a ten-year hold at a 6% cap rate, that $20,000 annual vacancy loss translates into roughly $333,000 of lost property value (capitalized). Reducing vacancy by even two percentage points can materially lift both cash flow and asset valuation.
When underwriting a rental property, most investors apply a vacancy allowance of 5%–10% of gross potential rent regardless of the historical occupancy. This conservative cushion protects against lease-up risk, seasonal softness, and unexpected turnover. The calculator's "lost rent" output is the reality check against that assumed allowance.
FAQ
How is rental property vacancy rate calculated?
Divide the total number of unit-months that were vacant by the total available unit-months (units × months in the period), then multiply by 100. For example, 12 vacant unit-months out of 144 total unit-months equals an 8.33% vacancy rate. This is the same formula used by property managers, appraisers, and the Census Bureau's residential vacancy survey.
What is the difference between vacancy rate and occupancy rate?
They are complements. Occupancy rate = 100% − vacancy rate. If your vacancy rate is 5%, your occupancy rate is 95%. Lenders and buyers typically quote occupancy rate for stabilized properties, while investors and property managers track vacancy rate because it directly maps to lost income.
How do I count vacant unit-months?
Add up every month each unit sat empty. If Unit A was vacant in January and Unit B was vacant in March and June, that is three vacant unit-months total. A single unit vacant for an entire year counts as 12. The count should include any period between tenants, units held for renovation, and units that were intentionally taken off the market.
What is a good vacancy rate for rental property?
Most healthy US multifamily markets run between 3% and 7%. Rates below 3% may indicate under-pricing (you could raise rents), while rates above 10% usually signal pricing, condition, or management problems. Always compare your rate to the local submarket average rather than a national number — some markets structurally run higher vacancy than others.
How much rent am I losing to vacancy?
Multiply your vacant unit-months by your average monthly rent. If you had 12 vacant unit-months and average rent is $1,000 per month, you lost $12,000 in rent. The calculator's "Lost Rent" output gives you this figure directly. This number is often called the "vacancy loss" line on a property's income statement.
Should I include units under renovation in the vacancy calculation?
It depends on purpose. For actual economic vacancy, yes — any unit not generating rent counts. For "physical vacancy" tracking, some managers separate renovation downtime from turnover downtime. For underwriting and lender reporting, include all units not producing rent, because that is the income you actually did not collect.
How does vacancy rate affect my cap rate and property value?
Vacancy reduces effective gross income, which reduces net operating income (NOI). Since property value roughly equals NOI divided by your cap rate, every dollar of avoided vacancy loss compounds into multiple dollars of asset value. A $10,000 reduction in vacancy at a 6% cap rate adds about $167,000 to property value.
Disclaimer
This vacancy rate calculator is provided for informational purposes only and does not constitute financial, real estate, or investment advice. Results are based entirely on the inputs you enter and the standard vacancy formula; actual vacancy rates, rents, and property values vary by market, property condition, tenant mix, and economic conditions. Always confirm your vacancy figures against your own leasing records and consult a licensed real estate professional or property manager before making investment decisions.