Garage Conversion Cost Calculator

In 2026, converting a garage into living space typically costs $50-$150 per square foot, so a single-car garage (~250 sq ft) runs about $12,000-$30,000 and a double-car garage (~450 sq ft) about $20,000-$60,000. A basic conversion (insulation, drywall, flooring, electrical) is at the low end, a fully finished living space with HVAC is mid-range, and a full ADU (accessory dwelling unit) with a kitchen and bathroom is the most expensive. The biggest cost drivers are adding plumbing (a bathroom or kitchen), HVAC, egress windows, and the finish level you choose.

A typical garage conversion includes: insulating the walls, ceiling, and floor (garages are usually uninsulated); framing and finishing interior walls with drywall; installing flooring over the bare slab (often after leveling or raising it to match the house); upgrading electrical (outlets, lighting, switches to code); extending heating and cooling to the space; and usually replacing the garage door with a framed, insulated wall (often with a window) so it looks like part of the house. More involved conversions add a bathroom, a kitchenette, and a separate entrance to create an ADU. Permits and inspections are required.

Yes, almost always. Converting a garage into habitable space is a change of use that requires building permits and inspections, covering framing, electrical, plumbing (if added), insulation, egress, ventilation, and smoke/CO detectors. Many areas also require that habitable rooms (especially bedrooms) have a code-compliant egress window. Zoning rules matter too: some municipalities restrict converting garages (particularly if it eliminates required off-street parking), and ADU conversions have their own rules. Converting without permits can cause problems with insurance, resale, and code enforcement. Check local building and zoning departments early — permitting can be a significant part of the timeline.

It can, but it depends on the market and execution. Adding finished, livable square footage — especially a legal bedroom, ADU, or in-law suite — often increases a home's value and can generate rental income. However, conversions that look like an afterthought, eliminate needed parking, or aren't permitted can hurt value, since some buyers want the garage for cars and storage. The best returns come from high-quality, permitted conversions that blend seamlessly with the home and add genuinely useful space (a real bedroom/bath or rentable ADU). In areas with high housing demand and ADU-friendly rules, garage-to-ADU conversions can be especially valuable; in others, losing the garage may be a drawback.

It depends on the intended use. For a simple bonus room, home office, gym, or playroom, you may not need either — keeping it to a basic finished room is far cheaper. For a bedroom or guest suite, a bathroom adds major convenience and value (about $8,000+). For a true ADU or rental unit, you'll need both a bathroom and a kitchen/kitchenette plus a separate entrance, which is what pushes the cost toward the high end. Plumbing is the most expensive part because the garage usually has no water/drain lines, so they must be run to the space — sometimes through the slab. Decide based on how the space will be used and whether it needs to function independently.

A straightforward garage conversion (basic finished room) typically takes about 2-4 weeks of construction, while a full living space with HVAC runs 4-6 weeks, and a complete ADU with a kitchen and bathroom can take 6-12 weeks or more. The overall timeline is usually longer because of permitting and design, which can add weeks to months before work begins, especially for ADUs or anything requiring zoning approval. Factors that extend the schedule include plumbing and electrical runs, raising or leveling the floor slab, custom finishes, and material lead times. Plan for the approval phase to be a significant, sometimes unpredictable, part of the project.

Usually both. Garage floors are typically a bare concrete slab that slopes toward the door for drainage and sits lower than the home's finished floor. For a quality conversion, the floor is often leveled and raised (with a subfloor or self-leveling compound) to match the house and eliminate the slope, then finished with flooring — and insulation is added since slabs are cold. The garage door is normally removed and the opening framed in as an insulated exterior wall, often with a window or door, so the converted room looks like part of the house rather than a garage. These two items — flooring/leveling and the door-to-wall conversion — are common, sometimes overlooked, parts of the budget.

Generally, yes. A garage conversion is usually cheaper per square foot than building a new addition because the structure already exists — you have the foundation/slab, walls, and roof, so you're mostly finishing the interior rather than building from the ground up. An addition requires new foundation, framing, roofing, and exterior work, making it more expensive. The trade-offs: you lose the garage (parking/storage), the converted space may have lower ceilings or a less ideal layout, and adding plumbing/HVAC to a garage can still be costly. If you have a garage you can spare and want to add living space economically, conversion is often the more budget-friendly route to extra square footage.