How this calculator prices a garage
Every line is an installed price, materials and labor together, taken from HomeGuide's itemized breakdown for a two-car detached garage and turned into rates a different-sized garage can use. The slab and the roof are priced per square foot of floor, the framing and siding per square foot of wall, the doors, windows and wiring per item, the gutters per foot of eave and the power feed per foot of trench. The low end of each rate comes from a 20 × 20 garage with 8 ft walls and the high end from a 24 × 24 with 9 ft walls, the two ends of HomeGuide's two-car range.
Because each part is priced on its own measure, the result moves the way a builder's quote does: taller walls raise the framing and siding but not the slab, a third door adds a door and an opener but nothing else, and a garage twice the floor area costs less than twice as much.
The range is wide because builder prices for the same garage are wide: the low and high ends of HomeGuide's itemized two-car breakdown are about three and a half times apart. Most quotes land well inside the band; the cost simulation above shows where the likely totals cluster.
How this compares with a flat per-foot price
HomeGuide's 2026 size table prices every detached garage at the same $50 to $100 per square foot: $14,400 to $28,800 for a 12 × 24, $20,000 to $40,000 for a 20 × 20, $28,800 to $57,600 for a 24 × 24 and $43,200 to $86,400 for a 36 × 24. A flat rate is a useful first check, but it cannot tell a bare shell from a finished building.
This calculator's unfinished garages land near the bottom of that table and its finished ones near the top. The difference is the interior: insulation, drywall and paint over the walls and ceiling are their own line items here, where a flat rate averages them in. Use the size tables below to see where your garage falls.
FAQ
How much does a detached garage cost in 2026?
A two-car 24 x 24 detached garage with 9 ft walls, two standard doors with openers, asphalt shingles, vinyl siding, basic wiring and an unfinished interior runs about $21,000-$52,800 installed at national average prices. HomeGuide's 2026 guide puts a two-car detached garage at $20,000 to $57,600. Size, the interior finish and how far power has to travel from the house move the price the most.
How much does a 1-car detached garage cost?
A 12 x 24 one-car garage with 8 ft walls, one door and opener, basic wiring and an unfinished interior runs about $13,400-$34,200 installed. HomeGuide's size table gives $14,400 to $28,800 for the same footprint.
How much does a 3-car detached garage cost?
A 36 x 24 three-car garage with 9 ft walls, three doors with openers, a subpanel and an unfinished interior runs about $29,200-$74,100 installed. HomeGuide's size table gives $43,200 to $86,400. Its table applies one $50 to $100 per square foot rate to every size; this calculator prices each part, and doors, wiring and the permit do not grow with the floor, so a bigger garage comes out cheaper per square foot.
What does a detached garage cost per square foot?
The default 24 x 24 garage works out to about $36-$92 per square foot installed, unfinished inside. A small garage costs more per foot than a large one because the doors, the wiring and the permit cost about the same whatever the floor area.
How much does it cost to finish the inside of a detached garage?
Insulating, drywalling and painting the walls and ceiling of a 24 x 24 garage with 9 ft walls adds about $4,000-$13,300. Insulation on its own adds about $1,400-$6,500. Finishing is the cheapest time to add outlets and lighting, before the walls are closed.
How much does it cost to run electricity to a detached garage?
Following HomeGuide, this calculator prices the wiring inside the garage at $1,600-$5,200, light fixtures at $70-$300, an optional subpanel at $500-$1,700 and the underground run from the house at $10-$25 per foot, so a 50 ft run adds $500-$1,250. If the house panel has no spare capacity, upgrading it is a separate job; see the electrical panel calculator.
Do I need a permit to build a detached garage?
Yes, almost everywhere. HomeGuide puts a building permit for a detached garage at $150 to $500, and electrical and plumbing work can need their own permits. Check setbacks and accessory-building height limits before you settle on a size: zoning, not cost, often decides how big the garage can be.
Is a detached garage more expensive than an attached one?
Usually a little, for the same size and finish. A detached garage has a fourth exterior wall to frame and side, and its power has to be trenched from the house rather than run through a shared wall. In exchange it keeps vehicle fumes out of the house and can sit wherever the lot and setbacks allow.
How much can I save building a garage myself?
In DIY mode the default garage comes to about $11,900-$30,400. That counts the builder trades (slab, framing, roofing, siding, doors, windows, gutters) at about half their installed price as materials, since HomeGuide puts labor at roughly half of a detached garage's cost, adds tool and equipment rental, and keeps the wiring at its installed price because it is licensed work. Permit fees are not counted in DIY totals. Many owners who frame their own garage still hire out the slab.
What does a garage workshop with a sink cost?
A 24 x 30 workshop with 10 ft walls, a metal roof, fiber cement siding, one insulated overhead door, four windows, a finished interior, a subpanel and a plumbed utility sink runs about $42,700-$104,600 installed, with moderate site grading. The sink itself is $450-$1,800 when a water line is close.
More questions
How big should a two-car garage be?
A 20 × 20 garage is the practical minimum for two cars and leaves little room to open doors or walk around them. A 24 × 24 fits two vehicles with space for storage along the walls, and a depth of 24 ft or more is worth it for a full-size pickup. Width matters more than depth for comfort: each extra 2 ft of width is room to open a door.
How long does it take to build a detached garage?
Once the permit is issued, a stick-built two-car garage usually takes a few weeks to two months: a few days for the slab and its cure, about a week to frame and dry in, then roofing, siding, doors and the electrical inspection. Weather, inspection scheduling and the wait for overhead doors are the usual delays.
Slab-on-grade or a frost wall?
Most detached garages sit on a monolithic slab with a thickened edge. In cold climates, or where the building official requires it, the perimeter needs footings below the frost line or a frost-protected shallow foundation, which costs more than the slab priced here. Ask your building department what it requires before you get quotes.
Pole barn or stick-built garage?
A post-frame (pole barn) building is often cheaper per square foot for large, tall, open spaces, and it goes up quickly. A stick-built garage on a slab matches a house more easily, finishes inside more simply and is what many neighborhoods and HOAs expect. For a large shop, price both with the pole barn calculator.
Can I add a room or apartment above it?
That is a different building. A habitable space needs stairs, egress, insulation, heating and often its own utilities, and it is usually zoned and permitted as an accessory dwelling unit. HomeGuide puts a detached garage with living space at $80,000 to $300,000.
