Run the numbers on your ADU
Three free calculators to pressure-test the money side of an accessory dwelling unit — from borrowing power to rental cash flow. Everything runs live in your browser; nothing is saved or shared.
Will your ADU pay for itself?
Model rental cash flow, cap rate, and the DSCR lenders look at. Best once you have a rough build cost and a target rent.
Will your ADU pay for itself?
Adjust the sliders to see cash flow, cap rate, and lender DSCR update live.
Construction, materials, labor, permits and fees.
Your upfront investment not covered by financing.
Expected rent for the finished unit.
Share of the year the unit is rented.
Estimate only.
Set to 0% if you self-manage.
Annual operating costs
Estimates for planning only — not a loan offer, appraisal, or guarantee of rental income. DSCR shown is a general guideline; lender requirements vary.
How much can future value unlock?
A renovation line lends against your home's value after the ADU is built. Compare that borrowing power to a standard HELOC on today's equity.
How much can future value unlock?
A renovation line lends against your home's value after the ADU is built. See how that compares to borrowing on today's equity.
Your home's appraised value today.
What you still owe on your first mortgage.
Total build cost you need to finance.
How much the finished unit is expected to raise your appraised value — often less than the build cost.
Estimate only — renovation lines often price above a first mortgage.
Lending limits (advanced)
Combined LTV an ARV-based program allows. Varies by lender.
Typical cap for a standard HELOC or home equity loan.
Estimates for planning only — not a loan offer, appraisal, or guarantee. Actual after-renovation value, loan-to-value limits, rates, and eligibility vary by lender, property, and borrower. CT ADU is not a lender.
Downsize and rent your main house
Move into a new ADU and rent the main home. Estimate the income that strategy could generate against your carrying costs.
What could renting the main house net you?
Move into a new backyard ADU, rent the larger main house, and see what's left after real-world costs. Adjust the sliders for your situation.
Asking rents across Fairfield County commonly run $5,000–$40,000; older homes in Greenwich, Darien, New Canaan and Westport often list around $10,000–$20,000.
Share of the year the home sits empty between tenants.
Set to 0% if you self-manage the tenant and repairs.
A large main house needs landscaping, snow removal, systems upkeep, and turnover work.
Landlord insurance and other carrying costs of renting the home.
What you pay to finance the ADU you move into. Set to 0 if paying cash.
Illustrative planning estimate only — based on asking rents, not signed leases, and not a guarantee of rental income. It does not include property taxes, income taxes, utilities you may cover, or major capital repairs. Confirm local rental rules and run the numbers with your CPA and lender before you build.
Every rate slider here is an assumption you set — not a quote. Actual rates, fees, loan-to-value limits, and after-renovation-value treatment vary by lender, property, and borrower. When you're ready for real numbers, we'll connect you with Connecticut lenders who understand ADUs.
The guides behind the math
Six ways to fund a CT ADU
HELOCs, renovation lines, construction loans and more — how each one works.
ADU ROI & rental income
What returns look like on a Fairfield County ADU, and how lenders read them.
HELOC vs. home equity loan
Which structure fits your equity, timeline, and first mortgage.
All calculators provide general estimates for planning only — not financial, tax, or lending advice, a loan offer, an appraisal, or a guarantee of rental income or value. CT ADU is not a lender or mortgage broker. Confirm all figures with a licensed lender and appropriate professionals.