Tools
Bay Area ADU cost calculator.
A real range for an ADU on your lot in 2026, based on size, build method, and city. Includes rental income and payback.
All-in build cost
$263K – $490K
Midpoint $377K · includes design, permit, factory or site build, foundation, install, and finish.
Estimated monthly rent
$3700/mo
Annual rental income
$44,520
Rough payback
8.5 years
How this is calculated. Modular estimates start with SHAPE's published Model 1, Model 2, and Model 2X prices, then account for size and city conditions. Site-built estimates use 2026 Bay Area ranges of $700 – $900/sq ft. Hillside and tight-access estimates use SHAPE's $400k – $750k typical range and may exceed it for larger or unusually complex sites. Rent uses current per-sq-ft rates for newly-built detached ADUs in each city. These are estimates; your real number depends on your lot, finishes, and current city fees.
