ADU Cost Calculator California 2025 | Cal Coast Construction

1 ADU Type

Junior ADU (JADU)

Within existing home, up to 500 sq ft

From $80,000

Garage Conversion

Convert existing garage to living space

From $120,000

Detached ADU

New construction, up to 1,200 sq ft

From $200,000

Attached ADU

Addition to existing home

From $175,000

2 Size

Select ADU square footage:

400 sq ft (Studio) 1,200 sq ft (2BR)

600 sq ft

3 Finish Level

Basic

Standard finishes, builder-grade

-15%

Standard

Quality finishes, popular choices

Base Price

Premium

Upgraded finishes throughout

+25%

Luxury

High-end, custom selections

+50%

4 Add-Ons (Optional)

Solar Panel System +$15,000

Mini-Split HVAC +$8,000

Deck/Patio +$12,000

Landscaping +$8,000

Attached Garage +$25,000

Smart Home Package +$5,000

Your Estimated ADU Investment

Base Construction $180,000

Permits & Fees $12,000

Design & Engineering $8,000

Site Work & Utilities $15,000

Add-Ons $0

Estimated Total Investment

$215,000 - $245,000

*Estimates based on 2025 California construction costs. Actual costs vary by location and site conditions.

Potential Monthly Rental Income

$2,100 - $2,800/mo

Based on average California ADU rental rates

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