ADU cost calculator
Estimate what your ADU will cost to build, with San Diego city fees and the site costs that catch people out. Based on builders' published 2026 prices.
Estimate
$341Kto$429K
About $514 per square foot
- Design, permits handling and construction$315K–$402K
- City of San Diego permit, capacity and school fees$26K
A planning estimate from builders' published 2026 San Diego prices, not a quote. Premium finishes, demolition and design changes cost more.
How the ADU cost estimate works
There's no official price list for ADUs, so the calculator uses the prices San Diego builders publish, and shows a range rather than a single number. Every input comes from a public source:
- Detached construction. Snap ADU's published San Diego all-in prices (March 2026): about $300K at 500 sq ft, $350K at 750, $425K at 1,000 and $450K at 1,200, on a level lot. We show 10% under to 15% over. Source
- Attached, garage and junior ADUs. Scaled from Lars Remodel's 2026 San Diego ranges: attached $200–350K+, garage conversion $150–225K+, junior ADU $120–200K+. Source
- City fees. Snap ADU's February 2026 table of City of San Diego plan check, permit, water, sewer and school fees by ADU size. Source
- Site costs. Snap ADU's San Diego site-work figures for meters, slopes, retaining walls, sewer pumps and sprinklers. Source
Fees outside the City of San Diego differ; untick the city box and check with your own city. For the full breakdown, read what an ADU costs in San Diego and ADU construction cost per square foot. Then get real quotes from verified ADU builders in San Diego.
Ways to bring the number down
- Keep it at 750 square feet or less to avoid impact fees anywhere in California, or under 500 to avoid school fees.
- Use a pre-approved plan to save design time and get a 30-day review.
- Convert existing space if it's sound; it avoids most site work.
- Compare three bids on the same plans, and keep payments tied to finished work. See how to hire an ADU contractor.