ADU budget estimator

This is a planning aid, not a quote. It multiplies your size by a median cost per square foot from California's statewide ADU owner survey, then adds soft costs and contingency using the ranges a San Diego public pilot reported. Every field is editable, so replace any default with a real number from a builder.

Type of ADUMedians from the California owner survey, published April 2021. Prices have likely risen since. Interior size, sq ft615 sq ft was the average new ADU in the same survey. Cost per sq ft ($)Changes with the type above. Overwrite it with a builder's number. Soft costs and fees (%)Design, surveys, engineering, permits and fees. In the San Diego pilot these plus contingency were 20 to 30 percent of the total. The survey's cost per sq ft already includes some design and permits, so we start low. Contingency (%)The San Diego pilot recommends 15 to 20 percent for ADUs. Rent per sq ft per month ($, optional)$3.68 was the median in the California owner survey.

-construction at your cost per sq ft

-with soft costs and contingency

-rough monthly rent at your rate

Not included: unusual site work such as street trenching, which added an estimated $100,000 on one San Diego pilot lot, or a panel relocation, which added about $10,000 per site there. Read what an ADU really costs and the five-project breakdown.

Sources: UC Berkeley Center for Community Innovation and Terner Center, Implementing the Backyard Revolution: statewide ADU owner survey (April 2021); San Diego Housing Commission, Accessory Dwelling Unit Pilot Program: Lessons Learned for San Diego Homeowners (October 2021).

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