Home Addition Cost Calculator
Per-SF cost from foundation, structure, and finish.
Inputs
%
Results
Total addition cost ($)
$76,713
Cost per sq ft ($)$256
Shell / structure ($)$39,000
Roofing tie-in ($)$4,000
Interior finishing ($)$7,500
HVAC extension ($)$3,000
Electrical ($)$1,500
Permits ($)$1,247
Design / engineering ($)$3,117
Contingency ($)$10,006
How to Use This Calculator
- Enter the addition square footage and select structure type (stick-built, modular, bump-out, or second story).
- Select foundation type (full basement, crawl space, or slab-on-grade).
- Set finish level and toggle bathroom addition to refine the estimate.
- Review total cost, shell cost, roofing, and finish costs broken out individually.
- Add permit, architectural, and landscaping costs to complete the total project budget.
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