ADU Cost Calculator (2026)
Get a 2026 budget range for your ADU in under 60 seconds. Calibrated to real permit fee schedules and builder bids across 16 US metros — including Los Angeles County, the Bay Area, San Diego, Denver, Houston, Phoenix, Portland, and Seattle.
Last updated: •Reviewed by the aduglossary editorial team
What the ADU Cost Calculator Does
The aduglossary.com cost calculator pairs three inputs — metro, ADU type, and size — with our 2026 build-cost model to give you an all-in budget range in seconds. It is designed for the moment before you talk to contractors: you want to know whether $200K, $300K, or $450K is the right number to plan around.
The model is rebuilt every quarter from three data sources: (1) public permit fee schedules in each supported metro, (2) Bureau of Labor Statistics construction labor cost indexes, and (3) recent builder bids submitted by users and partners. The output is a low-mid-high range that captures the spread between budget-conscious and premium builds in each city.
Use it to qualify financing, decide whether to size up to 800 sq ft, or compare a garage conversion against a detached new-build. It is not a substitute for two licensed contractor bids before signing a construction loan.
How to Use It
- Pick your metro. Pick the closest covered metro — LA, Bay Area, San Diego, Sacramento, Portland, Seattle, Denver, Phoenix, Scottsdale, Austin, Dallas, Houston, Charlotte, Raleigh, La Jolla, Oakland. The model adjusts for local permit fee schedules and labor markets.
- Choose ADU type. Detached new-build, attached, garage conversion, basement conversion, or above-garage. Type drives 30–50% of the cost spread.
- Enter size in square feet. 400–1,200 sq ft is typical. The calculator shows how cost-per-square-foot drops as size grows because of fixed permit and utility costs.
- Pick a finish level. Standard, mid-grade, or premium. Standard targets long-term rental ROI; premium targets owner-occupant or short-term rental positioning.
- Read the range. Output is a 3-tier range: budget-conscious, typical, and premium. Use the typical number for early planning; share the high number with your lender as a safety margin.
Sample Calculator Outputs (2026)
Here are typical results for a 600 sq ft detached ADU at a standard finish level across our supported metros — pulled directly from the calculator's model.
| Metro | Budget | Typical | Premium |
|---|---|---|---|
| Los Angeles | $240K | $310K | $420K |
| San Jose | $270K | $340K | $450K |
| San Diego | $228K | $295K | $380K |
| Sacramento | $180K | $240K | $310K |
| Portland | $210K | $275K | $360K |
| Seattle | $252K | $320K | $420K |
| Denver | $240K | $310K | $400K |
| Phoenix | $170K | $220K | $295K |
| Houston | $150K | $210K | $295K |
| Austin | $170K | $235K | $320K |
All-in including permits and soft costs. Excludes land, demo, and lot-specific work.
Ready to Run Your Numbers?
Open the calculator and get your budget range in under 60 seconds.
Launch the ADU Cost Calculator →Then compare loan options with the ADU loan calculator or browse financing options.
Pre-qualify With a Lender
Once you have a budget range, pre-qualify with one of our financing partners. Loan structure (HELOC vs. construction-perm vs. RenoFi vs. DSCR) often matters as much as the cost number.
Frequently Asked Questions
How does the ADU cost calculator work?
The calculator pairs your city, ADU type (detached, attached, garage, basement), size in square feet, and finish level with our 2026 cost model. The model is recalibrated quarterly using local permit fee schedules, BLS labor rates, and recent builder bids in 16 metros. Output is an all-in budget range including hard costs, soft costs, and permits.
What does the calculator include - and what does it leave out?
Includes: hard construction (labor + materials), design and engineering, project management, permits, and standard utility hookups. Excludes: land cost, demolition, lot-specific work like grading/retaining/soil remediation, and high-end appliances or smart-home upgrades beyond a basic finish package.
How accurate is the estimate?
Our 2026 model lands within +/-12% of contractor bids on typical projects in the 16 supported metros. Edge cases (sloped lots, historic districts, septic conversions, ADUs over 1,200 sq ft) skew higher. Always confirm with two licensed contractor bids before financing.
Can I use this calculator for Los Angeles County specifically?
Yes. Los Angeles is one of the calibrated metros. Pick LA from the city selector, then choose detached, attached, garage conversion, or above-garage. The calculator factors in LA Department of Building & Safety permit fees, school fees, and impact fee waivers for sub-750 sq ft units.
What is the difference between this calculator and a contractor bid?
This is a pre-bid budgeting tool - it tells you what to expect before talking to contractors. A contractor bid is site-specific and accounts for lot conditions you can't see in a model (foundation requirements, utility distance, soil class). Use the calculator to qualify financing; use contractor bids to commit to a budget.
Is the calculator free?
Yes. No signup, no email required. Optional lead capture if you want a personalized PDF or to be matched with a vetted contractor in your metro.
Related Guides
Got Your Financing? Now Manage the Build.
TerraLine connects your loan, budget, and schedule in one place. See exactly how much you've drawn, what's committed, and what's left — no spreadsheets needed.
Your Next Steps
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