Free ADU Cost Estimator
How Much Does an
ADU Cost?
Get an instant, location-adjusted estimate for your Accessory Dwelling Unit. Our calculator uses real construction data and regional pricing to give you a reliable starting point.
Free cost estimates
Updated Q1 2026
Trusted by 50,000+ homeowners
Why Use Our ADU Calculator?
Built with real construction data to give you the most accurate ADU cost estimates available.
Region-Adjusted Pricing
Costs adjusted for your state with real labor rates and permit fees, not one-size-fits-all national averages.
Real-Time Calculations
See your estimate update instantly as you adjust project details. No waiting, no page reloads.
Comprehensive Breakdown
See itemized costs for permits, design, foundation, and construction. Covers all 5 ADU types with detailed estimates.
Frequently Asked Questions
How accurate are these cost estimates?
Our estimates are based on real construction data and updated quarterly. They should be within ±15% of actual costs for most projects, but final costs depend on specific site conditions and contractor selection.
Are permit fees included in the estimate?
Yes, our estimates include typical permit fees scaled by your region and ADU type. However, some cities have unique requirements that may add additional costs.
What's not included in these estimates?
Site-specific costs like utility connections, significant grading, or structural upgrades to existing buildings are not included. These can add $5,000–$25,000+ depending on your property.
Which ADU types does the calculator support?
We support all five common ADU types: Detached ADU, Attached ADU, Garage Conversion, Junior ADU (JADU), and Basement Conversion. Each has different base costs, permit fees, and construction requirements.