ADU Tools & Calculators
Five free calculators that answer the questions a California homeowner asks before signing a contractor bid: can I build, what will it cost, what will it earn, which loan path makes sense, and is the project actually feasible. Each tool uses May 2026 rate data and field-tracked numbers across LA-area projects, calibrated quarterly. The free four take two to five minutes each. The paid Feasibility & Risk Assessment is a written report delivered in 3–5 business days. Sometimes the answer is not to build, and we say that clearly, before any money moves. ADUscale is an independent Owner's Representative, not a lender, contractor, or designer.
Which tool should you start with?
The five tools sit at different points in the homeowner process. The right starting point depends on where you are.
If you are unsure which one fits, the free Reality Check is the safest first move. It is the only tool that surfaces lot-level disqualifications (zoning overlay, coastal, fire-hazard zone, hillside) before you spend time on cost or financing math.
The five tools
Reality Check
What it does
Two-minute lot-eligibility check for any California single-family residential property. Pulls your county parcel data, runs it against current California state ADU law (Gov Code §65852.2) plus your city's local ordinance, and returns a one-page answer.
Inputs → Outputs
In: Property address, your situation (aging parent, rental income, home office), email for the report.
Out: Eligibility verdict (Yes / Yes-with-caveats / Likely-no), ADU types allowed, max size, setbacks, 2026 cost band, top three lot-specific risks, recommended next step.
What it doesn't do
Not a soils report, not a structural plan, not a permit submittal. It is the first answer, not the last word.
Cost Calculator
What it does
Estimates your total all-in California ADU cost using May 2026 labor rates, current city permit fee schedules, and field-tracked change-order categories that contractor bids typically leave out: utility upgrades, soft costs, contingency, permit fee variability, and site-condition premiums.
Inputs → Outputs
In: Address, ADU type, size in sqft, finish level (standard / premium / ultra).
Out: Low / median / high all-in cost band, per-sqft equivalents, soft cost breakdown, top three change-order risks for your specific lot, and a “what's not in the bid” callout.
What it doesn't do
Not a sales quote and not a contractor bid. It is a planning number to test bids against. Your specific contractor will issue the binding bid.
ROI Calculator
What it does
Models the financial return on a California ADU using May 2026 rate inputs (Federal Reserve H.15, Bankrate, FHFA National Mortgage Database). Companion to the Lock-In Calculator: ROI answers “does this project pencil at all;” Lock-In answers “which loan structure.”
Inputs → Outputs
In: Address, all-in construction cost, expected monthly rent, financing path, current primary mortgage rate.
Out: Gross yield, cash-on-cash return, monthly net cash flow, simple payback period, break-even rent, side-by-side vs. LA-area median.
What it doesn't do
Not a loan offer and not tax advice. ADUscale does not originate loans or provide investment advice. Your specific lender will issue a binding rate quote.
Lock-In Calculator
What it does
Compares two financing paths: keep your existing sub-5% primary mortgage and add a HELOC versus cash-out refinance the whole loan at 2026 rates. Roughly 80% of California homeowners hold a mortgage below 5% (FHFA National Mortgage Database), which makes this the single biggest financing decision in the 2026 rate environment.
Inputs → Outputs
In: Current loan balance, current interest rate, years remaining, approximate home value, ADU project cost, ADU type.
Out: 10-year and 30-year total cost comparison for Path A (keep + HELOC) vs. Path B (cash-out refi), the dollar difference, the threshold rate at which a refi would break even.
What it doesn't do
Not a lender quote. ADUscale is not a lender or mortgage broker. Your specific lender will issue a binding quote with exact rates based on your credit profile and property specifics.
$199 Feasibility & Risk Assessment
What it does
A 12–20 page written PDF report delivered in 3–5 business days. Not a calculator; the natural next step after the free tools when a homeowner wants a site-specific written answer. Includes lot analysis, ADU type recommendation, detailed cost model, financing-path recommendation, contractor-market read for your city, written risk register, and recommended next steps.
Inputs → Outputs
In: Address, situation, financing context. Order form on the product page.
Out: A written, signed PDF report you can use to make decisions. The $199 is the one upfront payment — the managed build that follows costs you nothing extra, same price as going direct. About 1 in 7 reports recommend not to build on this lot, in this market, with this budget.
What it doesn't do
Not a permit submittal, not an architectural drawing, and not a contractor contract. It is decision-support documentation — the written answer to “should I build, and if so, how.”
What none of these tools replace
A calculator estimates. It does not commit a contractor to a price, a lender to a rate, or a city to a permit.
A licensed contractor's bid
The Cost Calculator and ROI Calculator give you planning numbers. Before you sign anything, you need a written bid from a California-licensed contractor (CSLB Class B General Building or Class C specialty). The Cost Calculator's job is to give you the number to test that bid against, not to replace it.
A licensed CPA's tax filing
The ROI Calculator estimates depreciation and rental income at standard assumptions. Your specific tax outcome depends on your AGI, filing status, depreciation method, passive-activity rules, and California conformity items that a licensed CPA needs to confirm for your return.
A lender's binding rate quote
The Lock-In Calculator and ROI Calculator use published May 2026 rate ranges. Your actual rate depends on credit score, DTI, LTV, lender overlays, and the property's specifics. ADUscale is not a lender or mortgage broker.
We also do not run our 6-source contractor verification inside the free tools. That work happens only inside a paid Owner's Rep engagement, on the homeowner's lot, against their specific bids.
Tools & calculators — common questions
Yaro Korets — Founder of ADUscale
ADUscale is a California build-side ADU partner: we help homeowners secure one of the state's top contractors, expand that contractor's capacity to take the project, and protect the budget with inspection-gated milestone payments — at the same price as going direct. The five tools assembled on this page draw on the same underlying data used in the Feasibility & Risk Assessment: county parcel records (LA County Assessor, San Diego County Assessor, San Francisco Office of the Assessor-Recorder, and equivalent county systems statewide); current California ADU statutes (Gov Code §65852.2 and §65852.22); permit patterns from LADBS, San Diego DSD, and SF DBI; the InspectPilot 11M-record construction inspection database (2013–2026 California projects); current rate data from Federal Reserve H.15, Bankrate, and the FHFA National Mortgage Database; rental comp data from Zillow Rent Index and Apartment List; and California HCD permit-fee benchmarks. ADUscale is paid by the contractor out of his existing customer-acquisition budget — the homeowner pays the same price as going direct. ADUscale is not a lender, mortgage broker, financial advisor, contractor, or licensed designer; the tools on this page are informational. Your specific contractor, lender, and CPA will issue the binding numbers.
Last updated: June 2026.
Five tools. Start with the free Reality Check.
The free Reality Check is the cheapest, fastest entry point — and the one tool that flags lot-level disqualifications before you spend time on cost or financing math. If it returns a clean verdict, the Cost Calculator and ROI Calculator are the next two stops. The $199 Feasibility & Risk Assessment exists for the moment a written, site-specific answer is worth $199 to have in hand. Sometimes the right answer is not to build, and we say that clearly, before any further money moves.