Vacancy Rate Calculator
Enter vacant and total unit-days below to instantly get vacancy rate and effective gross income.
One unit for a year = 365; 4 units for a year = 1,460.
What Is Vacancy Rate?
Vacancy rate measures how much of a property's potential occupied time actually went unrented over a period, and effective gross income shows what that vacancy really costs in rental income.
Vacancy Rate = Vacant Unit-Days ÷ Total Unit-Days. Effective Gross Income = Gross Potential Rent × (1 − Vacancy Rate).
Worked example
A single-unit rental sat empty for 30 days out of a 365-day year, with $48,000 gross potential rent for the year.
Vacancy Rate = 30 ÷ 365 = 8.2%
Effective Gross Income = $48,000 × (1 − 8.2%) = $44,055
The same property with a longer, 60-day vacancy instead:
Vacancy Rate = 60 ÷ 365 = 16.4%, Effective Gross Income = $40,110 -- $3,945 less than the 30-day case, purely from the extra vacant month.
Common mistake
Running NOI and cap rate off gross potential rent instead of effective gross income. That skips a real, recurring cost of owning rental property and overstates every metric built from it.
Keep going
- Vacancy loss reduces the gross income that NOI starts from; the NOI calculator is where that adjusted income turns into a full operating-income figure. NOI Calculator
- A property's real-world vacancy rate directly affects whether it actually cash flows; the rental cash flow calculator is where that income ultimately nets out against expenses and debt. Rental Cash Flow Calculator
Frequently Asked Questions
What are "unit-days" and why use them instead of just days?
Unit-days multiply the number of units by the number of days, so a fourplex with one vacant unit for 30 days is 30 unit-days vacant out of 1,460 total (4 units × 365 days) -- a fair way to measure vacancy on multi-unit properties, not just single-unit ones.
What is effective gross income?
Gross Potential Rent × (1 − Vacancy Rate) -- the realistic income a property actually collects once vacancy is factored in, rather than the theoretical income if every unit were rented every single day of the year.
How does vacancy rate feed into NOI?
Effective gross income, not gross potential rent, is the honest starting point for NOI -- using gross potential rent without a vacancy adjustment overstates NOI and every ratio built on top of it.
What's a normal vacancy rate?
It varies a lot by market and property type -- a single-family rental in a tight market might sit near 0% most years, while a market-rate apartment building budgets for a real, ongoing vacancy rate between tenants. Check local market data rather than assuming a fixed number.
Should I use my property's actual historical vacancy or a market average?
For an existing property with real operating history, your own actual vacancy is the more accurate input. For a new acquisition with no history yet, a conservative market-average vacancy rate is the safer planning assumption.
This is a neutral calculation based on the numbers you enter -- not investment advice.
Related Calculators
- Gross Rent Multiplier Calculator — Quick Screening
- 1% Rule Calculator — Quick Screening
- Cap Rate Calculator — Return Metrics
- NOI Calculator — Income & Cash Flow