ADU Cost Calculator Utah

Estimate your ADU cost

Choose your ADU type, size, finish level, and market area below. You'll see an instant planning range — a low, typical, and high number — plus a breakdown of where the money goes. You don't need to enter an address or contact information to see your estimate.

How is this estimate calculated?

The calculator combines four things: a construction cost per square foot set by your ADU type and finish level; a separate allowance for design, permits, applicable fees, and utility work; a market-area cost adjustment; and a 10–15% contingency. The result is a planning range, not a bid.

Two things worth knowing about the math:

• Internal ADUs are not modeled with impact fees. An impact fee is a one-time charge a city levies on new construction to help pay for roads, sewer, and other infrastructure. Under Utah Code §11-36a-202, building an internal ADU inside an existing primary home is exempt from those fees. Detached and other projects may still owe impact and connection fees.
• Market area adjusts rough cost only. It does not decide whether an ADU is legal on your lot. That depends on your city and parcel — zoning, lot size, setbacks, utilities, and your local ordinance.

Cost inputs are aggregated from published 2026 Utah builder pricing and national construction databases adjusted for Utah's labor market, and the bands are reviewed quarterly. Regional adjustments are planning assumptions, not guaranteed local pricing.

What does this calculator estimate?

It estimates the all-in cost to build an ADU, not just construction. A good estimate separates hard construction from the soft costs, site work, utility work, and fees that quietly move the total — which is why two same-sized ADUs can cost very different amounts.

Here's how Utah ADU costs generally break down by type. Treat these as 2026 planning ranges, not quotes.

Want the full breakdown by type, city, and finish? See our Utah ADU cost guide.

Which type of ADU is usually cheapest in Utah?

Usually a basement or internal ADU, when your home already has workable space, ceiling height, and a path to a separate entrance. Detached units almost always cost the most because you're building a small house — new foundation, framing, roof, and utilities. There's also a rule that tilts the math toward internal units: they're exempt from impact fees.

Concept image; actual design, cost, and approval depend on site and local rules.

What makes your ADU cost more or less?

The line items below are where Utah ADU budgets actually swing. Finish level and square footage matter, but the surprises usually come from things you can't see at first — sewer distance, electrical capacity, grading, and life-safety work.

Use this as a hidden-cost checklist before you request any quotes:

• Utility distance and capacity: How far are sewer, water, gas, and power from the build site? Does your electrical panel have spare capacity? Long trenching and a panel upgrade can add thousands. (A utility hookup is the connection of the ADU to water, sewer, power, and gas.)
• Basement egress and life-safety work: Internal ADUs often need a code-compliant egress window, a separate entrance, ceiling height, fire separation, and ventilation.
• Detached site work: Grading, foundation, drainage, and tight equipment access raise detached costs fast.
• Finish level: Basic rental-grade vs. premium kitchens, flooring, and fixtures is one of the widest single swings.
• Parking: Some cities require an added off-street space for an ADU; a garage conversion may require replacing the parking you removed.
• Separate metering: Some Utah cities require an ADU to share the main home's utilities and don't allow a separate meter, especially for internal ADUs. Where it is allowed, it adds cost. Verify before you assume.
• Market: Costs tend to run higher in Salt Lake County and the Park City / Summit-Wasatch area, and lower in rural Utah.
• Contingency: Budget 10–15% on top. A real project almost always finds something.

What Utah rules can change your estimate — and your feasibility?

A Utah ADU's cost isn't just construction math; zoning and code can change whether the project pencils at all. The biggest fork is internal vs. detached, because the state treats them very differently. And no matter the type, a legal ADU requires applicable local permits and code compliance — don't treat any ADU path as permit-free.

Internal ADUs (inside your existing home)

Utah law (§10-21-303 for cities, §17-80-303 for counties; formerly HB 82) makes an internal ADU a permitted use in most residential zones — meaning a qualifying unit is allowed by right, without a discretionary hearing. The state-regulated internal-ADU category is defined as a habitable unit created within an owner-occupied single-family home, inside its existing footprint, for a rental term of 30 consecutive days or longer. Internal ADUs are exempt from impact fees (§11-36a-202) — one of the biggest financial advantages. Cities can still regulate design, parking, rental licensing, short-term rental, and lot size.

Detached ADUs (a separate backyard structure)

The specific threshold of 11,000 sq ft is a floor — cities that already allow detached ADUs on smaller lots can keep doing so. The "specified municipality" definition covers most incorporated cities; some smaller towns fall outside it. Treat your city's adopted ordinance as the thing you actually build against.

Rules that apply to most ADUs

• Owner occupancy — Many Utah cities require the owner to live in either the main home or the ADU (Salt Lake City does). This matters for investors hoping to rent both units. (Owner occupancy = the property owner uses one of the units as their primary residence.)
• Short-term rental — Often restricted or prohibited for ADUs; cities regulate nightly/Airbnb-style use separately. Don't assume it's allowed.
• HOA rules — For a compliant internal ADU, a homeowners association generally cannot prohibit renting it. Detached ADUs are different: an HOA's covenants can still restrict or block a detached unit even when city zoning allows it.

Why your city matters

Because so much turns on your specific city and lot, here are a few verified examples of how the rules differ. This is a sample, not a full inventory — confirm your own city and parcel.

The calculator flags these factors rather than pretending to clear them. The feasibility review is where they get checked against your address.

How accurate is this ADU cost calculator?

It's accurate enough for early budgeting and choosing a path — not accurate enough to sign a contract. A real bid requires a site review, a defined scope, plans, utility confirmation, and contractor pricing. We deliberately show a range, because precision you can't back up is just a guess in a nicer font.

What should you do after you get your estimate?

The next step usually isn't "hire a builder." It's confirming your likely ADU type, your rule constraints, and your rough budget so that any future quote is based on a realistic scope. Match your result to the right move:

When you're ready, we can take your inputs, check feasibility against your actual property, sharpen the estimate, and — only if it makes sense — point you to local estimate options. You can verify any contractor's license yourself through Utah DOPL before work begins.

Utah ADU cost calculator FAQ