Home Addition Cost Calculator
Estimate the cost of adding a room, second story, sunroom, or ADU to your home. Calculate by project type, square footage, quality level, and foundation. Get a detailed cost breakdown including foundation, framing, finishing, permits, and contingency. Free, no sign-up required.
Enter your own cost per square foot for a custom project.
Ground-level additions need a foundation. Second stories and garage conversions typically do not.
🏠 Estimated Total Cost
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Addition Size
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Cost / Sqft
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Construction
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Soft Costs
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📊 Cost Breakdown
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Costs vary by region, contractor, and project complexity. Always obtain professional quotes.
💡 What this means
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🛠 Get renovation tools & supplies
🛠 See renovation tools on Amazon →📝 How to use this home addition cost calculator
- Select addition type — bedroom, bathroom, kitchen, living room, second story, sunroom, garage conversion, ADU, or custom.
- Enter dimensions — the length and width of the planned addition in feet. The calculator multiplies them for total square footage.
- Choose quality level — basic (vinyl flooring, stock fixtures), mid-range (laminate, semi-custom), or luxury (hardwood, custom cabinetry, high-end finishes).
- Select foundation — slab, crawlspace, or full basement. Second-story additions and garage conversions typically do not need a new foundation.
- Toggle options — add plumbing and electrical for wet rooms, include permits and plans, and add a 15% contingency buffer for unexpected costs.
- Click Calculate — see total cost, cost per square foot, and a detailed breakdown.
📌 5 tips for planning a home addition
- ✓ Get 3+ contractor bids. Addition costs vary 40-60% between contractors for the same scope. Ensure each bid includes foundation, framing, electrical, plumbing, drywall, finishes, permits, and a payment schedule in writing.
- ✓ Check zoning and setback rules first. Before designing, visit your local planning department to confirm your lot can accommodate the addition. Setback requirements, height limits, and lot coverage caps can kill a project before it starts — and the check is free.
- ✓ Plan for the disruption. A ground-level addition often means weeks without use of adjacent rooms, dust throughout the house, and temporary relocation of furniture and utilities. Budget for temporary kitchen or bathroom use if those rooms are affected.
- ✓ Match the exterior to the existing home. Siding, roofing, windows, and trim should blend seamlessly. Mismatched additions look like afterthoughts and hurt resale value. Order materials at the same time to avoid color and texture mismatches from different production batches.
- ✓ Include a 15-20% contingency. Unforeseen issues — rot, outdated wiring, soil problems, code upgrades — surface once walls are opened. A contingency fund prevents project-stopping cash shortfalls and lets you make change orders without stress.
Disclaimer: This calculator provides estimates for educational purposes only. Actual home addition costs vary significantly based on location, soil conditions, existing home structure, contractor rates, material choices, local building codes, and project complexity. Always obtain professional quotes from licensed general contractors and structural engineers before making budget decisions. This tool is not a substitute for professional construction advice.
Related Tools
A home addition is a major investment that touches every part of your property. These twelve calculators cover the rest of your home improvement and ownership costs — from roofing and siding to renovation budgets and financing.
- Home Renovation Cost Calculator — estimate total renovation costs across multiple project types to budget your addition within a full home update.
- Kitchen Renovation Cost Calculator — if your addition includes a kitchen, estimate the fit-out cost separately for a detailed budget.
- Roof Replacement Cost Calculator — tie the addition's roof into your existing roof and estimate materials and labor costs.
- Siding Cost Calculator — estimate siding for the addition's exterior walls to match your home's existing siding.
- Drywall Calculator — estimate drywall sheets, mud, tape, and screws for the addition's interior walls and ceiling.
- Flooring Cost Calculator — estimate flooring costs for the addition's interior to match or complement existing floors.
- Paint Calculator — estimate gallons of paint for the addition's interior and exterior walls.
- Square Footage Calculator — measure your lot and existing home to confirm setback room for the addition.
- Home Equity Calculator — see how much equity you can borrow against to finance your addition.
- Home Insurance Calculator — recalculate your coverage needs after adding square footage to your home.
- Insulation Calculator — estimate R-value and insulation needs for the addition's walls, ceiling, and floor.
- Home Maintenance Cost Calculator — budget annual upkeep for your larger home after the addition is complete.