Skip to main content
ADU Cost Authority · All 50 States

The ADU you've
imagined — backed
by real data.

Real construction cost data, permit guides, and ROI analysis for every U.S. market. Free. No signup. Built by homeowners who wished they'd had this first.

Nationwide CoverageCurrent Cost ResearchPermit GuidanceROI Analysis
50+ State cost guides
6 ADU types covered
±15% Accuracy target
Free No account needed
Instant Estimate
Instant Cost Estimate
Estimated Project Cost
Select a state
Typical range · ±15% accuracy · not a contractor bid
Why trust these numbers?
Planning estimates — not contractor bids
Built from regional labor, permit & material data
Updated June 2026 · No contractor advertising
±15% accuracy target across all 50 states and Washington, DC
Why This Resource Exists

The number that matters
comes before the bid.

Most homeowners talk to contractors before they understand what ADUs cost in their market. That information asymmetry is expensive. This site exists to close it — with real regional data, not national averages that mislead 80% of the people who read them.

Browse All 50 State Guides →
📍

Regional, not national

Construction costs in Memphis and Manhattan differ by 3×. Our data is built from local labor rates, permit records, and regional multipliers — not averaged into meaninglessness.

🏗️

Type-specific pricing

A garage conversion costs half what a detached new build costs. We break down all six ADU types with separate cost models — because the type changes everything.

📋

Permits explained, honestly

We cover what your city actually requires, how long it takes, what it costs, and what trips people up. Not a generic checklist — specific to your market.

💰

ROI you can model

Local rental rates, payback periods, and property value impact by city. The data you need to make the investment decision before you commit to anything.

ADU Costs by State

Every market is different.
Find yours.

All 50 states →
ADU Investment Returns — National Averages
$1,200
Median monthly rental income (national)
10–14
Typical payback period in years
+22%
Avg. property value increase
$3,000+
Monthly rental income in top markets
Calculate My ROI →
Homeowner Feedback

Used across every U.S. market.
Trusted before the first call.

50+
State cost guides published
6
ADU types with separate cost models
±15%
Accuracy target vs. final contractor bids
Free
No account, no paywall, no contractor pitch

I used NationwideADU before talking to a single contractor. When the bids came in, I knew immediately which ones were fair and which were inflated. The California guide was exactly what I needed.

MR
Michael R.
San Diego, CA · Detached ADU

The permit section for Texas was the first place I found honest timelines — not the optimistic version contractors tell you. Saved me from a contractor who quoted 8 weeks for a 6-month permit city.

LT
Laura T.
Austin, TX · Garage Conversion

Finally — a site that breaks costs down by ADU type, not just "ADUs cost $150K-$400K nationwide." The Colorado guide had numbers that matched what I actually paid within 12%.

JK
James K.
Denver, CO · Basement Conversion
Types of ADU

Which type fits
your property?

Full comparison →
Modern detached ADU backyard cottage with cedar siding and warm interior lighting at dusk
01 / Detached ADU
Detached ADU
$80K – $420K

Freestanding backyard structure with maximum privacy and rental flexibility. The most common ADU type nationwide — and the highest rental income potential.

  • Fully independent living unit
  • No shared walls with primary home
  • Strongest long-term property value impact
Detached ADU Guide →
Garage converted to a fully furnished ADU living space with glass door at sunset
02 / Garage Conversion
Garage Conversion
$42K – $185K

The most affordable ADU path in most markets. The existing structure eliminates foundation and framing costs — and speeds permit approval in most cities.

  • Lowest total project cost
  • Fastest permit approval pathway
  • Best for immediate rental income
Garage Conversion Guide →
Finished basement ADU with walk-out patio, living room, and kitchen at dusk
03 / Basement Conversion
Basement Conversion
$50K – $200K

Turns unused basement space into a fully rentable unit. Most cost-efficient in the Midwest and Northeast where full basements are standard in older housing stock.

  • Year-round construction possible
  • No exterior footprint added to your lot
  • Often the fastest indoor ADU path
Basement ADU Guide →
Modern two-story attached ADU addition with wood siding and large windows at sunset
04 / Attached ADU
Attached ADU
$78K – $315K

An addition to the primary home sharing one wall. Best for smaller lots where backyard detached construction isn't feasible — and ideal for multigenerational living.

  • Works on smaller urban lots
  • Shares structural elements — lower cost
  • Ideal for multigenerational households
Attached ADU Guide →
Modern prefab modular ADU in a backyard with floor-to-ceiling glass walls at dusk
05 / Prefab & Modular
Prefab / Modular
$65K – $280K

Factory-built and crane-installed on your prepared foundation. The fastest construction timeline of any ADU type — and increasingly cost-competitive with stick-built in many markets.

  • Fastest path to rental income
  • Factory quality control
  • Cold-climate rated units available nationwide
Prefab ADU Guide →
Simple ADU Planning Process

Four steps. No
surprises.

Most ADU projects stall not from budget issues, but from not knowing what comes next. Here's the sequence that works.

01
Know your market cost
Use our state guides to understand what ADUs realistically cost in your city — before you talk to anyone.
02
Check your permit path
Verify your zoning, setbacks, and permit timeline. Surprises here are expensive. Our permit guide covers your specific market.
03
Model the ROI
Run the numbers — payback period, rental income, and property value impact — before you commit to a single dollar.
04
Get 3 contractor quotes
Armed with real cost data, you can evaluate bids with confidence. Compare apples to apples — not hope to hype.
Ready to Build?

Get 3 free estimates from licensed ADU builders near you.

  • No obligation — compare and decide
  • Licensed, insured contractors only
  • Takes 2 minutes. Free.
Your Project
Get My 3 Free Quotes →

By clicking, you agree to receive contractor outreach for your project. No spam. Unsubscribe anytime.

Ready to Find Out?

What will your ADU
actually cost?

Start with your state guide. Free, no signup, no contractor pitch. Just the data you need to plan with confidence.

Our Estimates Contractor Quote
Purpose Budget before you build Price for your specific project
Based on Regional averages ±15% Your site conditions
Best used Before talking to contractors After you know the market
Cost Free — always $0–$500 for estimate