Short answer: Start at 5% of rent (about 18 empty days a year), or your city's Census ACS rental vacancy if it is higher. FirstDoor market pages use max(5%, city ACS). Stress-test 8–10% for longer turns. ACS 2024 puts the US rate near 5.7%; Census HVS reported 7.3% nationally in Q2 2026.
Definition
Vacancy rate is the share of potential rent you do not collect because the unit sits empty — roughly days vacant ÷ 365, or lost rent ÷ gross potential rent.
By the numbers: Census ACS 2024 puts US rental vacancy near 5.7%. FirstDoor defaults to 5% and uses max(5%, city ACS vacancy) on market pages. Census HVS reported 7.3% nationally in Q2 2026. See all 50 markets.
What vacancy rate means
Vacancy rate is the share of potential rent you do not collect because the unit sits empty (or sometimes because of concessions). For a single rental, the cleanest definition is:
Vacancy rate ≈ days vacant ÷ 365Lost rent ≈ gross potential rent × vacancy rateAt FirstDoor's 5% default, that is about 18 days empty a year — roughly one turnover with a couple of weeks of freefall between tenants. On a $2,000/mo rent, 5% is $100/mo of lost rent built into the model before you ever see cash flow.
Good to know: Market vacancy (Census ACS or HVS) measures empty units across a city or the country. Your property's effective vacancy can be higher after a bad tenant, a slow lease-up, or a rehab — so treat Census rates as a floor for underwriting, not a guarantee.
What Census data shows
Two official surveys measure rental vacancy differently. Use both as context, then underwrite your own unit.
| Census ACS 2024 (US) | Rental vacancy about 5.7% (FirstDoor markets data from ACS table B25004). City rates in the 50 largest renter markets range from about 3.0% (San Jose, CA) to 12.6% (Atlanta, GA). |
| Census CPS/HVS (Q2 2026) | National rental vacancy 7.3% — not statistically different from Q2 2025 (7.0%) and virtually the same as Q1 2026 (7.3%). HVS is the quarterly headline rate used in economic indicators; it is not the same survey as ACS. |
| City examples (ACS 2024) | Chicago about 3.7%; Houston about 12.0%. Tight coastal and Midwest cities often sit under 5%; several Sun Belt metros sit well above it. |
Red flag: Copying a national average into every deal. A 5% budget in a 12% vacancy market understates empty months; a 0% assumption anywhere ignores turnover.
FirstDoor's 5% default (and market pages)
FirstDoor's calculator defaults to 5% vacancy so empty months are not a surprise on a first rental. On market pages, the scored typical home uses max(5%, the city's ACS rental vacancy) — so Chicago (3.7% ACS) still underwrites at 5%, while Houston (12.0% ACS) underwrites at 12%.
Lenders often take a similar haircut another way: Fannie Mae's selling guide counts only 75% of gross rent on a purchase before subtracting the full payment (PITIA). That 25% stand-in covers vacancy and maintenance — stricter than a 5% vacancy line alone.
Tip: Start at 5% (or your city's ACS rate if higher), then stress-test 8–10% if you expect longer turns, seasonal demand or a first-time lease-up. See methodology for the exact OpEx formula.
How vacancy hits cash flow
Vacancy is modeled as a percent of rent, so it lowers effective income, cap rate, cash-on-cash and DSCR together. Same $200,000 house at $2,000/mo, 20% down at 7.40% (Freddie Mac average, October 15, 2026), FirstDoor defaults otherwise (5% maintenance, 8% management):
| Vacancy | Cash flow | Cash-on-cash | DSCR |
| 0% | $332/mo | 8.7% | 1.30 |
| 5% | $232/mo | 6.1% | 1.21 |
| 8% | $172/mo | 4.5% | 1.16 |
| 10% | $132/mo | 3.4% | 1.12 |
Going from a rosy 0% to FirstDoor's 5% cuts cash flow by about $100/mo and cash-on-cash from 8.7% to 6.1%. At 10% (about 36 empty days a year), cash flow falls to about $132/mo and cash-on-cash to 3.4%.
Tip: Try the same listing at different vacancy % in the rental cash-flow calculator or the full deal score. Pair it with estimating rent — an optimistic rent plus 0% vacancy is a double miss.
How to choose a rate
1. Look up your city on FirstDoor markets (ACS 2024 rental vacancy) or the Census ACS tables.
2. Underwrite at at least 5%, or the city ACS rate if it is higher — matching how FirstDoor scores market pages.
3. Add a stress case at 8–10% for turnover, seasonality or a first lease-up after rehab.
4. Do not confuse a short listing-site "availability" rate with your long-run lost rent; one empty month is already ~8% of a year.
5. Keep cash reserves for the gap between tenants — vacancy % in the model does not magically fund paint, cleaning and showing time.
Good to know: This is educational, not investment advice. Your effective vacancy depends on tenant quality, pricing, season and how fast you can re-lease.
Worked example
A $200,000 single-family rental at $2,000/mo, 20% down at 7.40% for 30 years (Freddie Mac average, October 15, 2026), $2,400/yr tax, $1,200/yr insurance, 5% maintenance, 8% management. Closing costs assumed at $6,000. Vacancy varied; ACS 2024 US rental vacancy is about 5.7%. Illustrative deal so vacancy swings are easy to see.
| Rent | $2,000 |
| Vacancy @ 5% | −$100 |
| Operating costs @ 5% vac | −$660 |
| Mortgage (P&I) | −$1,108 |
Frequently asked questions
What vacancy rate should I use for a rental property?
Start at 5% of rent (about 18 empty days a year), or your city's Census ACS rental vacancy if it is higher. FirstDoor market pages use max(5%, city ACS). Stress-test 8–10% for longer turns. ACS 2024 puts the US rate near 5.7%; Census HVS reported 7.3% nationally in Q2 2026.
How do you calculate vacancy rate?
Divide days vacant by 365, or divide lost rent by gross potential rent for the year. At $2,000/mo rent, a 5% vacancy allowance is $100/mo of lost rent in the model — about 18 empty days if the unit is either full or empty.
Why does FirstDoor default to 5% vacancy?
Five percent builds in a normal turnover without pretending every month is collected. On market pages FirstDoor raises that to the city's ACS rental vacancy when ACS is higher (for example Houston at about 12.0% ACS underwrites at 12%). Lenders often haircut rent more aggressively — Fannie Mae counts 75% of gross rent on a purchase.
Keep learning
Sources
Educational content, not financial advice. Loan programs and requirements change; confirm with a lender.