ADU Cost Calculator

Based on your inputs and real ADU projects in California
Plot
ADU
Site
Cost
Results
Basic information about the plot
Estimate your ADU project costs based on key factors
City / county:
*Some cities have higher permitting and construction overhead, which can affect total project cost and timeline.
Plot Type
*Lot shape and layout influence construction logistics and cost efficiency.
Property Access:
Construction Access:
*Limited construction access may increase labor time and equipment costs.
Construction of an Accessory Dwelling Unit (ADU) can be a smart move - whether you are a homeowner who wants to expand your home, an investor who wants to increase your property value, or a contractor who wants to estimate costs. One of the most common inquiries is: how much will it cost? Our ADU Cost Calculator is created to give you a realistic, fact-based estimate for your specific project goals.

ADU Cost Calculator

Based on your inputs and real ADU projects in California
Plot
ADU
Site
Cost
Results
ADU Type and Size
This selection affects construction scope and cost only. ADU type eligibility depends on zoning and site conditions.
ADU Type
*Standalone ADUs are typically more expensive than conversions due to new foundations, utilities, and structural work.
Square Footage: 340 sq ft
100 sq ft
1, 200 sq ft
Larger ADUs require more materials, labor, and engineering—this increases the total cost but often lowers the price per square foot.

ADU Cost Calculator

Based on your inputs and real ADU projects in California
Plot
ADU
Site
Cost
Results
Slope
Factors that influence cost
Finish level:
Slope of the plot:
Balanced quality and price (chosen by most owners)
*Sloping plots complicate the foundation and drainage — on average, this adds +25% to the cost.
Utility Connection Distance:
*Longer utility runs require trenching and coordination, increasing construction cost.
These factors affect construction cost only and do not confirm site feasibility.

View your ADU cost range and feasibility insights

Based on typical project assumptions. Final cost depends on site verification and design.
Plot
ADU
Site
Cost
Results
Conservative
Standard conditions, minimal site complexity
Cost range:
$xxx,xxx – $xxx,xxx
Cost per sq.ft:
$xxx,xxx
Most Likely
Typical ADU project based on similar builds
Cost range:
$xxx,xxx
Cost per sq.ft:
$xxx,xxx
Higher Complexity
Slope, utilities relocation, premium finishes
Cost range:
$xxx,xxx
Cost per sq.ft:
$xxx,xxx – $xxx,xxx
What this estimate assumes
Standard site conditions
No major utility upgrades
Typical permitting path
No unusual zoning overlays
$xxx,xxx – $xxx,xxx
*Exact numbers are shown after unlocking your results
Conservative
Most Likely
Higher Complexity
Effective cost per sq.ft
~ $XXX / sq.ft
Estimated timeline:
~ $XXX / sq.ft
Includes design, permits, and construction
Based on 120+ ADU projects in California
Updated quarterly using real permit data
Used by homeowners in LA, SD, SF

Your Estimated ADU Cost Range

Based on your inputs, location, and common project assumptions, this range reflects realistic ADU construction costs — not a contractor quote.
Conservative
Standard conditions, minimal site complexity
Cost range:
$240,000 – $360,000
Cost per sq.ft:
$240,000 – $360,000
Most Likely
Typical ADU project based on similar builds
Cost range:
$240,000 – $360,000
Cost per sq.ft:
$240,000 – $360,000
Higher Complexity
Slope, utilities relocation, premium finishes
Cost range:
$240,000 – $360,000
Cost per sq.ft:
$240,000 – $360,000
What drives your cost
ADU type
Size
Finish level
Site factors
What this estimate does NOT include
Zoning approval
Survey results
Utility capacity confirmation
Final architectural design
$240,000 – $360,000
Conservative
Most Likely
Higher Complexity
Effective cost per sq.ft
~ $700 / sq.ft
Estimated timeline:
9–12 months
Includes design, permits, and construction
Based on 120+ ADU projects in California
Updated quarterly using real permit data
Used by homeowners in LA, SD, SF
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Estimate Your ADU Costs Easily

The ADU building price is highly variable depending on size, materials, location, and labor. Our ADU calculator simplifies this by employing industry averages and recent pricing trends to make it simple for you to:
01
Plan your budget with greater accuracy
02
Understand which elements influence cost the most
03
Compare options like detached ADUs, garage conversions, and above-garage units
04
Save time on manual calculations and  guesswork
Instead of vague ballpark figures, you get a tailored estimate that can guide key decisions early in the planning process. We at ADU Pro will be happy to help you with this.

Cost to Build a Garage Calculator for Effective Comparison and Planning

Thinking about turning your garage into an ADU or building a new one from the ground up? Our cost to build a garage calculator makes it easy to figure out what it might cost. Just plug in a few details and get an instant estimate that covers everything from framing and roofing to insulation, garage doors, and any structural upgrades you might need. Whether it's a simple conversion or a full-on build with living space above, the calculator gives you a clear view of where your money's going and how to make the most of what you already have.

Factors That Affect ADU Costs

The ultimate cost of an ADU is not a one-size-fits-all figure. Here are the most important cost drivers:
Type and Size of the ADU
  • Detached ADUs (built separately from the main house) are usually more expensive due to foundation and utility hookups.
  • Garage conversions tend to be more affordable since the structure already exists.
  • Above-garage ADUs require structural reinforcement, which adds to costs.

Size matters too. More square footage means more materials, labor, and permitting.

Materials and Finishes

The materials you choose significantly impact cost:

  • Basic materials (vinyl flooring, laminate countertops) keep costs low
  • Premium finishes (hardwood floors, stone counters) raise the budget

Also consider framing, roofing, insulation, and HVAC systems. Our ADU cost calculator accounts for material choices so you can see how upgrades affect your total.

Labor and Contractor Rates
Labor costs vary based on your location and job size. You can expect to pay more for skilled labor in areas with greater demand or stricter building codes. Local contractor availability can also influence scheduling and costs.
Permits and Design Fees
Architectural plansand permits are required - and they don't come cheap. They can range anywhere from $3,000 to $15,000 or more in your locality. Impact fees for new structures are also charged by some local governments.
Utility Connections
It may cost several thousand to connect an ADU to existing sewer, water, gas, and electrical lines. Independent meters are sometimes required in certain situations and are an additional cost.
Site Conditions
Uneven land, limited access for construction equipment, or existing structures that need demolition can increase costs. A flat, accessible lot is usually cheaper to build on.

How Our ADU Cost Calculator Works

Our tool asks a few simple questions about your:
  • Property type and location
  • Desired ADU size and layout
  • Materials and finish level
  • Whether you're converting an existing garage or building from scratch
It then generates a detailed cost breakdown. You can try different scenarios and immediately see how changes affect the total. Whether you're building a backyard cottage or upgrading a garage, the cost to build a garage calculator feature is integrated to make comparisons easy.

Financing Your ADU: Try Our ADU Loan Calculator

Worried about how to finance your project? The ADU loan calculator helps you understand loan options based on current interest rates, project cost, and down payment. Whether you're using a home equity loan, construction loan, or refinance strategy, this tool helps you:
01
Compare loan types and monthly payments
02
Estimate payback periods
03
Assess rental income potential for investment-focused builds
An ADU can generate between $1,500 to $3,000/month in rental income depending on your market. Our ADU loan calculator lets you evaluate ROI before you commit.

Get Started with ADUSCALE Today

Ready to make the most of your property? Whether you're thinking about a small home ADU, a tiny home, or a fully detached ADU, we’re here to help.
Get My Cost Estimate