ADUCostGuide · Free Tool · Updated 2026

ADU Cost Calculator

Estimate what it costs to build an accessory dwelling unit in your state — itemized like a contractor's bid.

600 sq ft

Most states cap ADUs between 800–1,200 sq ft. Studios start around 300.

Estimate sheetCA · Detached · 600 sq ft
  • Construction & materials
  • Design & engineering
  • Permits & city fees
  • Utility connections
  • Site work & contingency
Estimated total range
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Estimates reflect 2026 national cost data adjusted by state labor and permit indexes. Actual bids vary with lot conditions, utility distances, and city-specific fees — treat this as a planning range and confirm with local licensed contractors. See our city guides for permit rules and fees where you live.