Accessory Dwelling Unit (ADU) Calculator

ADU ImageWhat is an ADU?

An accessory dwelling unit (ADU) is a secondary housing unit on a single-family residential lot. ADUs have been known by many names: granny flats, in-law units, backyard cottages, secondary units, and more. According to the California Department of Housing and Community Development (HCD), ADUs are an innovative, affordable, and effective option for adding housing. It has grown exponentially in number as more cities and counties become interested in ADUs as one solution to increasing the supply of affordable housing. ADUs can be built on new construction, as a conversion of part of the home, modular, and more. 

How does the ADU Calculator work?

The ADU Calculator is a generated tool that estimates the cost of converting part of your home or constructing a rental unit. To effectively utilize the ADU calculator, input the information on the physical characteristics of the planned ADU. This will determine possible monthly expenses, rent, and development costs. The cost varies by local jurisdiction. 

Please visit the San Joaquin County’s ADU Calculator.


  1. Christine Tran-NEW

    Christine Tran

    Assistant Regional Planner