Home Addition Cost Calculator
Estimate the total cost of a home addition project, including materials, labor, permits, and design fees.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Home Addition Cost Calculator
This tool estimates the total cost of a home addition based on size, quality, and complexity. All inputs are in imperial units (square feet) and US dollars.
- Enter Square Footage – Input the total area of the addition in square feet (e.g., 500).
- Select Quality Level – Choose Basic ($150/sqft), Standard ($200/sqft), or Premium ($300/sqft).
- Set Number of Stories – Enter how many floors the addition will have (minimum 1).
- Choose Complexity – Pick Simple (+0%), Moderate (+10%), or Complex (+25%) to adjust for construction difficulty.
- Add Fixed Costs – Enter amounts for Permits & Fees and Design/Architect Fees (defaults provided).
- Set Contingency – Input a percentage (0–50%) for unexpected costs (default 10%).
- Click "Calculate Cost" – The total and detailed breakdown will appear below.
Formula: Total = (Base Construction + Complexity Adjustment + Permits + Design) × (1 + Contingency%)
All fields are validated; ensure non-negative numbers and square footage greater than zero.
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Frequently Asked Questions
Costs depend on square footage, quality of materials, number of stories, complexity of design, permits, architect fees, and contingency.
This calculator provides a rough estimate based on average national costs. Actual costs may vary by location, labor rates, and specific project requirements.
Contingency is a percentage added to cover unexpected costs during construction. A typical range is 10-20% of the subtotal.