ADU Directory
Cost Guides

ADU Cost Guides

Real pricing data from verified builders, broken down by size, state, and type. Updated quarterly with line-item costs and per-sqft benchmarks.

$60k–$520k typical$150–$600 / sqft16 guides

By Size

Cost per square foot drops as the build grows.

400 Sq Ft ADU Cost
$130k–$200k
$325–$500 / sqft
500 Sq Ft ADU Cost
$150k–$240k
$300–$480 / sqft
600 Sq Ft ADU Cost
$175k–$280k
$290–$470 / sqft
700 Sq Ft ADU Cost
$200k–$320k
$285–$460 / sqft
800 Sq Ft ADU Cost
$220k–$360k
$275–$450 / sqft
900 Sq Ft ADU Cost
$245k–$390k
$270–$435 / sqft
1000 Sq Ft ADU Cost
$270k–$420k
$270–$420 / sqft
1200 Sq Ft ADU Cost
$320k–$500k
$265–$415 / sqft

By State

Labor, permits, and impact fees vary widely.

California ADU Cost
$200k–$500k
$280–$600 / sqft
Washington ADU Cost
$180k–$420k
$250–$500 / sqft
Oregon ADU Cost
$160k–$380k
$230–$460 / sqft
Massachusetts ADU Cost
$220k–$480k
$290–$580 / sqft

By Type

Conversions are cheaper than new detached builds.

Garage Conversion ADU Cost
$90k–$200k
$200–$400 / sqft
Prefab ADU Cost
$130k–$300k
$180–$350 / sqft
Detached ADU Cost
$200k–$500k
$280–$500 / sqft
JADU (Junior ADU) ADU Cost
$60k–$150k
$150–$350 / sqft