Plan your ADU with real numbers.
Free calculators for homeowners thinking about adding an accessory dwelling unit: a backyard cottage, garage conversion or in-law suite. See what it could cost, what it could rent for and how long it takes to pay for itself.
ADU calculators
Every calculator is free to use, works on your home computer or phone, and needs no sign-up.
Cost & budget
ADU Cost Calculator
Detached, attached, garage conversion or junior ADU. A cost range with permit and design fees.
Coming soonGarage Conversion Cost Calculator
What it costs to turn your garage into a living space.
Coming soonFinancing & income
ADU Financing Calculator
Monthly payments for a HELOC, home equity loan or cash-out refinance.
Coming soonADU Rental Income & Payback Calculator
Estimated rent, expenses and the years it takes to earn back your build.
Coming soonState guides
California ADU Guide
State rules, permit fees and typical costs for California homeowners.
Coming soonHow it works
Three steps from idea to a plan you can take to a builder.
- Describe your projectThe type of ADU, its size and where you live.
- See your numbersEstimated cost, monthly payment, rent and payback time.
- Talk to buildersWhen you're ready, compare quotes from builders in your area.
What is an ADU?
An accessory dwelling unit is a second, smaller home on the same lot as a house. It has its own kitchen, bathroom and entrance. It can be a detached backyard cottage, a converted garage, an addition, or a unit inside the main house. Homeowners build them to earn rental income or to house family members, and a growing number of states now require cities to allow them.