How to Estimate a Multifamily Buildout (Per-Unit and Per-Square-Foot Math)

Multifamily Cost Per Square Foot and Per Unit (2026)

The $/unit number is what lenders, equity, and owners read first. The $/sf number is what estimators bid against. They have to reconcile — divide one by the other and you get average unit size, which is the simplest sanity check on whether the program matches the budget.

The Cost Stack on a Multifamily Estimate

Multifamily estimates roll up across six major cost buckets. The percentages below are typical for a 30-unit garden-style project. Mid-rise and high-rise shift the percentages toward structure and MEP and away from finishes.

How to Build the Estimate Step by Step

1. Verify the program against the gross/net ratio

Owners specify net rentable square feet. Estimators bid gross construction square feet. The ratio between the two depends on building type — garden-style efficiency runs 85–88%, podium runs 78–84%, mid-rise runs 72–80%. Use the wrong ratio and your $/sf benchmark applies to the wrong number. On a 30,000 nrsf garden project, a 5-point efficiency miss is 1,800 sf of unbilled construction cost.

2. Lock the unit mix early

Unit mix drives finish cost, plumbing fixture count, and bedroom-to-bath ratios. A 30-unit project with 30% studios costs less per unit than the same building with 30% three-bedrooms. Get the unit mix in writing before pricing finishes. Carry a mid-mix assumption (typical: 20-30-40-10 split across studio/1BR/2BR/3BR) until the architect confirms.

3. Price MEP from the rough-in count, not the square footage

Plumbing fixture count is the lever on plumbing cost. Each unit carries a kitchen, a bath (or two), an HVAC condensate line, and a laundry hookup. A 30-unit project with two-bath units has 50% more plumbing rough-in than the same building with one-bath units. Same with electrical — outlet count, panel size, and meter bank scale to unit count, not building square footage.

4. Carry site work as its own bid

Site work on multifamily often lands 25–40% over initial budget on garden-style projects. Soil conditions, stormwater requirements, and offsite improvements (curb cuts, sidewalks, utility extensions) are rarely fully drawn at bid time. Get the civil sub on a site walk before pricing, not after.

5. Reconcile to per-unit cost before submitting

Total hard cost divided by unit count is the lender's first sanity check. If your number lands outside the typical $/unit range for the building type, find out why before submitting. Either the program is unusual (good), the spec is rich (good if owner expects it), or the bid is wrong.

The Six Most Expensive Misses on Multifamily Bids

• Sprinkler scope on a Type IIIA-over-Type IA podium. The wood frame above and the concrete podium below have different sprinkler requirements and the transition floor needs special attention. $30K–$80K easy to miss on a 30-unit project.
• Sound attenuation in demising walls and floor assemblies. Code requires STC 50 / IIC 50 minimums in most jurisdictions. Premium assemblies (resilient channels, gypcrete, mass-loaded vinyl) run $4–$8/sf of demising area. Budget assemblies fail inspection.
• Window flashing and weather-resistive barrier (WRB) coordination. Improperly detailed WRB-to-window transitions are the #1 cause of multifamily envelope warranty claims. Carry $0.50–$1.50/sf of envelope just for the detail labor.
• Stormwater management and bioretention. Most jurisdictions now require on-site stormwater retention. A 30-unit project typically needs $40K–$120K of bioretention basins, underground detention, or permeable paving — rarely fully drawn at schematic.
• Common area finishes. Lobbies, mail rooms, fitness centers, leasing offices, and amenity spaces run $80–$140/sf of common-area square footage on a mid-tier multifamily — far above the unit cost. Verify what's in the program.
• Final cleaning and turnover punch. $300–$600 per unit for final clean, $400–$800 per unit for punch list completion. Forgotten on rush bids; non-negotiable on delivery.

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FAQs

What is the typical cost per unit for multifamily construction in 2026?

Garden-style wood-frame multifamily typically runs $160K–$250K per unit in 2026. Podium construction (3-over-1 or 5-over-2) runs $240K–$380K per unit. Mid-rise and high-rise climb from $340K to $700K+ per unit depending on construction type, finish tier, and metro market. Per-unit cost is driven primarily by building type and unit size, not finish level alone.

What's the biggest cost-driver on multifamily that estimators underestimate?

Site work and stormwater management. Civil scope on multifamily routinely lands 25–40% over initial budget because soil conditions, offsite improvements, and stormwater retention are rarely fully drawn at bid time. Get the civil sub walking the site before pricing, and carry a contingency on civil specifically that's separate from project contingency.

How does GC fee work on multifamily projects?

Multifamily GC fee tracks the standard project-size curve — 4–6% on $5M–$15M projects, 3–5% on $15M–$50M, 2.5–4% above $50M. CM-at-risk and design-build delivery typically shave 1 point off lump-sum fees because risk is shared. See the GC fee benchmark report for the full breakdown.

What's the difference between hard cost and total development cost?

Hard cost is construction only — what the GC bids. Total development cost adds soft costs (architecture, engineering, permits, legal, financing, marketing) plus land acquisition. Soft costs typically run 20–30% on top of hard cost. Land is its own number. Lenders evaluate total development cost; GCs bid hard cost.