Free estimate — verify against local code before building
Garage Cost Calculator
Estimate a transparent attached or detached garage planning range from visible editable assumptions.
What this calculator includes
This garage cost planner separates slab, structural and exterior shell, interior finish, overhead doors, electrical work, site and permit allowances, and contingency. The editable low, expected, and high scenarios expose what is included without pretending to determine structural design, fire separation, zoning feasibility, or an exact local contractor price.
Next step in your project
Plan the garage approach and driveway connection
Use the measured driveway footprint, pavement section, base, demolition, reinforcement, labor, and contingency assumptions.
Open Concrete Driveway Cost Calculator →How to use this garage cost calculator
- 01
Enter the outside footprint
Use the planned outside length and width, then enter stories separately so slab and total floor area are not confused.
- 02
Define the building scope
Choose attached or detached, enter complexity, and make slab, shell, and interior-finish assumptions visible.
- 03
Count doors and systems
Add overhead-door, electrical, site, and permit ranges rather than hiding them inside a single square-foot number.
- 04
Replace allowances progressively
Update the scenarios as survey, sitework, plans, supplier pricing, utility requirements, and comparable proposals become available.
Worked example
Example: 24-by-24 detached garage
A 24 ft by 24 ft one-story detached garage with two overhead doors, editable slab and shell rates, no interior-finish rate, an electrical allowance, site and permit allowance, and 15% contingency produces category-specific low, expected, and high scenarios.
Practical buying and overage guidance
Compare proposals against the same drawings and schedule for excavation, slab, framing, roof, siding, doors, windows, insulation, fire separation, electrical, heating, drainage, site restoration, permits, cleanup, warranty, exclusions, and concealed-condition terms.
Calculation sources and review
Primary references and formula assumptions are linked so you can verify them against the selected product, supplier, and adopted local requirements.
Internal formula review completed July 13, 2026. What this review covers
- U.S. Census Bureau - Characteristics of New Housing (opens in a new tab)
National characteristics do not determine local garage cost; all rates remain editable.
- American Wood Council - Design for Code Acceptance (opens in a new tab)
Structural and connection requirements need an approved project-specific design.
- OSHA - Electrical (opens in a new tab)
Electrical work presents serious hazards and requires appropriate qualified design and installation.
Frequently asked questions
Does garage square-foot cost include the slab?
In this calculator the slab is a separate visible category, so it is not silently embedded in the shell rate. Match all categories to the written proposal before comparing totals.
Is an attached garage always cheaper?
No. The default attachment factor is only editable planning logic. Tie-in, fire separation, occupied space, roof geometry, utilities, access, demolition, and finish matching can reverse the difference.
Does the estimate include a finished room above the garage?
Only entered stories and finish rates are represented. Egress, stairs, structure, insulation, HVAC, plumbing, fire separation, and living-space requirements need their own scope and design.
Are electrical outlets and vehicle charging included?
Only the editable electrical allowance is included. Service capacity, feeder, lighting, receptacles, door operators, heating, and vehicle charging require load review and qualified electrical work.
Does this verify zoning, foundation, or structural design?
No. Property limits, setbacks, lot coverage, soils, frost, drainage, loads, foundations, fire separation, permits, and utility requirements are site-specific.