Home Addition Cost Calculator

Estimate the cost of building a home addition with our room addition cost calculator. Adding square footage to your home is one of the most significant construction projects a homeowner can undertake, and accurate cost estimation is essential for budgeting and financing. Our tool helps you estimate costs for various addition types including bedroom additions, family room expansions, second story additions, sunrooms, and in-law suites.

Home addition costs are typically calculated on a per-square-foot basis, but the actual cost per square foot varies considerably based on the type of space being added. A basic room over an existing foundation costs less than a ground-floor addition that requires new foundation work, excavation, and roofing. Additions that include plumbing, such as bathrooms or kitchens, cost more due to the complexity of extending utility lines.

Our calculator lets you specify the addition size, type, foundation requirements, and finish level. It estimates costs for foundation and framing, roofing, exterior finishing, insulation, drywall, flooring, electrical, HVAC extension, plumbing if applicable, windows and doors, and interior finishing. The tool also accounts for architectural and engineering fees, permit costs, and the often-overlooked expense of matching the addition's exterior to your existing home. Plan your addition project with confidence using realistic cost ranges before engaging contractors for detailed bids.