What does DU/AC mean?

Dwelling Units per Acre. The standard multifamily density metric.

How do I convert lot area per unit to DU/AC?

DU/AC = 43,560 ÷ (lot area per unit in SF). E.g., 1,815 SF/unit ≈ 24 DU/AC.

Are density bonuses automatic?

No — they require meeting specific requirements (affordable set-asides, sustainability targets) and often a formal application.

What's a typical multifamily density?

Suburban garden-style: 18–30 DU/AC. Urban mid-rise: 60–150 DU/AC. Urban high-rise: 200+ DU/AC.

Density Calculator

Residential density — units per acre — is the multifamily equivalent of FAR: the zoning number that caps how many homes you can put on a site. Getting to your maximum allowable density (with density bonuses, if available) usually determines whether a deal pencils.

Enter total units and site acreage to compute density in units per acre — the standard multifamily zoning metric.

How density is regulated

Zoning codes express density as either 'maximum units per acre' (e.g., 24 DU/AC) or 'minimum lot area per unit' (e.g., 1,800 SF/unit). The two are interchangeable — 24 DU/AC ≈ 1,815 SF/unit.

Density bonuses

Many jurisdictions offer bonuses of 20–50% above base density for affordable-housing inclusion, transit proximity, senior housing, or sustainability. Density bonuses often drive the deal — a 24 DU/AC base becomes 35 DU/AC with a 45% affordable bonus.

Effective vs. gross density

Gross density uses total site area. Net density excludes streets, easements, and required open space. Some codes use gross, others net; the two can differ by 20% or more on a site with heavy infrastructure requirements.

Density and unit mix

Density caps unit count, not unit size. You can hit maximum density with 500 SF studios or 1,500 SF three-bedrooms. Unit mix drives revenue, construction cost per unit, and marketability — pick the mix your submarket demands.

Density and product-type feasibility

Density thresholds correspond directly to construction typology. Under 18 DU/AC almost always means detached single-family or duplex product. 18–30 DU/AC supports garden-style walk-ups with surface parking. 30–60 DU/AC pushes you into three-to-four-story wrap or podium construction. 60–120 DU/AC typically requires structured parking and Type III-A wood over podium or Type I concrete. 120+ DU/AC generally requires concrete or steel high-rise. Each jump in typology roughly doubles the construction cost per unit relative to the tier below it. High density is only economical when land cost per unit is high enough to justify the construction premium — expensive land in dense urban markets, cheap suburban land almost never.

Parking as effective density cap

Zoning-permitted density and physically achievable density often diverge because parking requirements consume site area. A 2.0 spaces-per-unit surface-parking requirement can cap effective density around 30 DU/AC no matter what the zoning ordinance says — the site simply runs out of room for asphalt. Structured parking removes that ceiling but costs $25,000–$50,000 per stall for above-grade and $50,000–$85,000 per stall for below-grade. Parking-reduction incentives (transit proximity, affordable set-asides, bike infrastructure) are often the difference between a feasible and infeasible dense project.

Density calculations by lot type

Verify whether your jurisdiction measures density on the gross parcel, net buildable area after right-of-way dedications, or net after private streets and easements. Large sites with public street dedications can lose 15–25% of gross acreage to right-of-way before density is calculated. Always model both gross and net density during due diligence; a site advertised at 'permitted for 60 units' can shrink to 48–52 units once dedications and required stormwater areas are accounted for.

Worked Example

Example: 2.4-acre site zoned for 20 DU/AC. Base density: 48 units. Add a 35% affordable bonus: 48 × 1.35 = 64.8, rounded down to 64 units. Setback and coverage will still shape the building form, but 64 units is the top-line target for the pro forma.

Common Mistakes

• Confusing gross density with net density. • Skipping available density bonuses. • Rounding density up instead of down. • Ignoring open-space and parking requirements that eat effective density.

How It Works

Step 1 — Density = Total Units ÷ Site Acres.
Step 2 — Compare to the zoning code's maximum allowed density.
Step 3 — For SF-based zoning, divide site square footage by minimum lot size per unit.

Frequently Asked Questions

What does DU/AC mean?: Dwelling Units per Acre. The standard multifamily density metric.
How do I convert lot area per unit to DU/AC?: DU/AC = 43,560 ÷ (lot area per unit in SF). E.g., 1,815 SF/unit ≈ 24 DU/AC.
Are density bonuses automatic?: No — they require meeting specific requirements (affordable set-asides, sustainability targets) and often a formal application.
What's a typical multifamily density?: Suburban garden-style: 18–30 DU/AC. Urban mid-rise: 60–150 DU/AC. Urban high-rise: 200+ DU/AC.

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