How to Estimate Vacancy for a Rental

When you evaluate a rental, the first line you write after gross rent is the vacancy allowance. It is the cushion you give yourself for months when the unit sits empty, for turnover, or for rent‑loss due to tenant issues. Getting that number right separates a realistic cash‑flow projection from an optimistic sales pitch.

What a vacancy rate is

The vacancy rate is the percentage of potential gross income that you expect to lose because the unit is not occupied. It is expressed as a share of the annual scheduled rent, not of the market rent. In practice you apply the rate to the gross scheduled income (GSI) to arrive at an effective gross income (EGI). The formula is simple:

Because vacancy is a cost, it reduces the cash flow that the property can generate. It also impacts derived metrics such as cap rate, cash‑on‑cash, and debt service coverage ratio.

The 5% default — where it comes from

Many industry templates default to a 5 % vacancy allowance. That figure is a rule‑of‑thumb derived from decades of aggregated data across the United States. It assumes a relatively stable market where a typical unit is vacant for about 18 days per year. The 5 % number also aligns loosely with the average turnover cost (roughly one month of rent per two‑year tenancy). While convenient, the default should be treated as a starting point, not a final answer.

Worked example: the same deal at 5% and 7%

Let’s walk through a concrete example using only the numbers supplied in the brief. The property rents for $1,800 per month, yielding $21,600 per year in scheduled rent. The purchase price is $250,000. Operating expenses (taxes, insurance, maintenance, management) total $8,088 per year. Debt service on a typical loan is $15,967 per year.

Step 1 – Calculate vacancy loss

Step 2 – Effective gross income (EGI)

Step 3 – Net operating income (NOI)

Step 4 – Cash flow after debt service

Derived ratios

Cap rate is NOI divided by purchase price.

Turnover: the cost beyond the empty month

Vacancy loss does not capture the full expense of a tenant moving out. You also incur a make‑ready cost: cleaning, repainting, minor repairs, and advertising. In our example the make‑ready cost is $500. Adding one month of lost rent ($1,800) gives a total turnover cost of $2,300 per vacancy.

If the average tenancy lasts two years, the annualized turnover cost is $2,300 ÷ 2 = $1,150 per year. Compared to the scheduled rent of $21,600, that is roughly 5.3 % of rent—coincidentally close to the 5 % vacancy allowance.

Finding your local rate

To move beyond the 5 % default you need local data. Sources include:

• U.S. Census Bureau’s Housing Vacancy Survey.
• Local MLS or property‑management reports.
• Historical rent rolls for the specific building.

When you have a local vacancy percentage, replace the 5 % or 7 % input in the tables above and let the spreadsheet recalculate the downstream figures. The same workflow is described in our How to Calculate NOI guide and the How to Analyze a Rental Property guide.

Stress test: one empty month (8.3%)

A simple stress test assumes a full month of vacancy. One month out of twelve is 1 ÷ 12 = 8.33 % vacancy. Applied to the $21,600 scheduled rent, the loss is $1,800 per year. The resulting cash flow would be:

The cash‑flow gap widens by $720 compared with the 5 % scenario, illustrating how a single empty month can materially affect profitability.

The verdict

Using the 5 % vacancy assumption, the property yields a cap rate just under 5 % and a negative cash flow of $3,535 per year. Raising the vacancy assumption to 7 % pushes cash flow down another $432 per year and drops the cap rate to 4.80 %. The turnover cost analysis shows that a 5 % allowance is not arbitrary—it mirrors the annualized cost of replacing tenants every two years.

Vacancy vs rent growth: the trade-off

Raising the rent on a $1,800/month unit looks attractive because a $100/month increase adds $1,200 to the annual cash flow. In theory that extra income improves the deal, but only if the unit remains occupied. The moment a month slips into vacancy, the $1,800 loss wipes out the benefit of that $100 raise for 18 months, effectively erasing the gain you thought you earned.

Even a modest vacancy rate can nullify the upside. At a 5% vacancy level the property loses $1,080 each year, which is almost the entire $1,200 you would have earned from a $100 increase. Push the vacancy to 7% and the annual loss climbs to $1,512, surpassing the rent‑rise benefit entirely. Those figures show why one extra empty month is more damaging than a steady $100 bump.

The real cost shows up when a tenant leaves. A turnover cost $2,300, composed of one empty month at $1,800 and $500 for make‑ready work. That $2,300 hit is already double the $1,200 you hoped to capture from the rent hike, and it occurs before the new rent even takes effect. When you factor in vacancy loss and turnover expense together, the safest path often remains modest rent growth paired with strong tenant retention.

Run your own numbers

The workflow above is exactly what our spreadsheet automates. Start with the free Lite version of the Real Estate Deal Analyzer — the main analyzer sheet with cap rate, NOI, cash flow, cash‑on‑cash, DSCR and the 1% rule check. If you screen deals regularly, the Full version adds a sensitivity grid, a 5‑year projection with IRR, a BRRRR calculator, a 3‑deal comparison sheet, and a 15‑point due‑diligence checklist. Both are on the Real Estate Deal Analyzer page.

This guide is an educational calculation aid, not financial, tax, or legal advice. Verify all figures against local data and consult licensed professionals before purchasing any property.