What will it cost to build an ADU?

Our ADU Calculator is a great place to start when developing a budget. It provides a rough estimate of costs and income and will help you understand how choices can impact your budget over time. In general, it is helpful to avoid having a fixed budget total in your head as you explore your options.The cost to build an ADU typically ranges from $30,000 for a simple interior conversion JADU, to $400,000+ for a large detached ADU with high-end finishes on a hillside lot. Cost per square foot is a good way to estimate, though this too can range — a very rough placeholder for you to use is $400-700 per square foot for construction and other costs (design, fees, etc.), depending on your design and the materials you chose.

See more details about costs – including design, permitting, and construction – in our ADU Workbook. Also see our blog post on 5 hidden costs.