ADU Cost Calculator

Estimate your Accessory Dwelling Unit (ADU) construction costs and calculate ROI based on expected rental income. Get a complete cost breakdown and break-even analysis.

Total square footage of the ADU

Prefab typically costs less per sq ft

Construction cost per square foot (prefab: $150-250, custom: $250-400+)

Permits, impact fees, utility connections

Estimated monthly rental income

Total Cost = (ADU Size x Cost/Sq Ft) + Permit Fees | Monthly ROI = (Monthly Rent / Total Cost) x 100 | Break-Even Years = Total Cost / Annual Rent
For a 600 sq ft prefab ADU at $200/sq ft with $5,000 permits: Total Cost = $125,000. At $2,000/month rent: Monthly ROI = 1.92%, Break-even in 5.2 years

How much does it cost to build an ADU?

ADU construction costs typically range from $150 to $400 per square foot depending on construction type, location, and finishes. Prefab/modular ADUs tend to cost less ($150-$250/sq ft), while custom-built ADUs can range from $250-$400+/sq ft. Local labor costs, permit fees, and site preparation also affect total cost.

What is the ROI on an ADU?

ADU ROI depends on construction cost and rental income in your area. Typical ADUs generate $1,000-$3,000/month in rent. At $2,000/month rent with a $150,000 build cost, you could break even in about 6.25 years. Many homeowners see 5-10% annual ROI plus property value appreciation.

Do I need permits to build an ADU?

Yes, ADUs require building permits in most jurisdictions. Many states have passed laws streamlining ADU approvals to address housing shortages. Permit costs range from $1,000-$10,000 depending on location and project scope. Check your local zoning laws and building codes before starting.

What is the difference between prefab and custom ADUs?

Prefab (prefabricated) ADUs are built off-site in a factory and installed on your property, typically costing less and completing faster. Custom ADUs are designed and built on-site, offering more design flexibility but at higher cost and longer timelines. Prefab ADUs can save 20-40% compared to custom builds.