What will it cost to build an ADU?

The 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. Visit our ADU Calculator.

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 from $200–$400 per square foot depending on the complexity and finishes of your project. $300 per square foot is a good starting estimate for an average project.

See more details about costs – including design, permitting, and construction – in our Guidebook.