Construction estimator - Updated June 2026
Home Addition Cost Estimator
Use our free home addition cost estimator and calculator to get an instant estimate before breaking ground. Select your addition type, size, foundation, finish level and US location to calculate home addition cost based on real 2026 contractor rates.
Enter your addition details
Select your addition type and size
Make your selections on the left to calculate your home addition cost estimate instantly.
- Most 300 sqft bedroom additions cost $50000-$80000
- Bathroom and kitchen additions cost the most per sqft due to plumbing
- Second story additions skip foundation cost but require structural reinforcement
- Permits are required in nearly all US jurisdictions for additions
What affects home addition cost?
- Addition type - Bathrooms and kitchens cost far more per square foot than bedrooms due to plumbing and electrical needs.
- Foundation - A full basement adds significant cost but provides valuable extra square footage.
- Second story vs ground floor - Building up skips foundation costs but requires structural engineering and temporary roof removal.
- Tying into existing structure - Matching rooflines, siding and finishes to your existing home adds complexity that new construction does not have.
- Size - Fixed costs like foundation and permits are spread over more square footage as the addition grows, often making larger additions better value per square foot.
- State - Labor costs in California and New York run 25-30% higher than Midwest states.
How much does a home addition cost in 2026?
The average home addition cost in 2026 ranges from $80 to $600 per square foot, with most projects falling between $150 and $350 per square foot. A typical 300 sq ft bedroom addition costs between $50000 and $80000 including foundation and standard finishes. Use our free home addition cost estimator calculator above to get an instant, personalized estimate based on your addition type, size and US state.
Home addition cost calculator - by addition type
The type of room you are adding is one of the biggest factors in total cost, primarily because some rooms require significantly more plumbing, electrical and appliance work than others. Our home addition cost estimator calculator adjusts pricing automatically based on your selected addition type.
| Addition type | Cost per sq ft | 200 sq ft | 400 sq ft | 600 sq ft |
|---|---|---|---|---|
| Garage | $74-$160 | $15000-$32000 | $30000-$64000 | $44000-$96000 |
| Sunroom | $105-$220 | $21000-$44000 | $42000-$88000 | $63000-$132000 |
| Bedroom | $135-$285 | $27000-$57000 | $54000-$114000 | $81000-$171000 |
| General room / office | $140-$295 | $28000-$59000 | $56000-$118000 | $84000-$177000 |
| Family room | $148-$315 | $30000-$63000 | $60000-$126000 | $90000-$189000 |
| ADU / in-law suite | $200-$420 | $40000-$84000 | $80000-$168000 | $120000-$252000 |
| Kitchen addition | $220-$465 | $44000-$93000 | $88000-$186000 | $132000-$279000 |
| Bathroom addition | $265-$560 | $53000-$112000 | $106000-$224000 | $159000-$336000 |
Second story addition cost calculator
Adding a second story is one of the most transformative and expensive types of home addition, typically costing $200 to $500 per square foot. Building up doubles your living space without expanding your home's footprint, making it ideal for smaller lots. Costs run higher than ground floor additions because the project requires temporary roof removal, structural reinforcement of the existing first floor, a new staircase, and full extension of HVAC and electrical systems. For a 1000 sq ft second story, expect to invest $220000 to $320000 at standard finish levels.
Estimate home addition cost calculator - what is included
- Foundation - Slab, crawl space or full basement as selected (not applicable for second story additions)
- Framing - Wall, floor and roof framing tied into your existing structure
- Exterior finishes - Siding, roofing and windows to match your existing home
- Interior finishes - Drywall, flooring, paint and trim at your selected quality level
- Labor - All construction labor across every trade involved
The estimate does not include land surveys, major structural reinforcement to the existing foundation, or significant landscaping beyond basic restoration. Plumbing, HVAC, electrical panel upgrades, permits and landscaping are available as add-ons in our calculator above.
Frequently asked questions
How accurate is this home addition cost estimator?
Our home addition cost estimates are typically within 15-25% of actual contractor quotes for standard projects. Additions that involve significant structural changes, historic homes, or difficult site access can vary more widely. Always get at least 3 quotes from licensed general contractors before committing to a budget.
How do I estimate home addition costs?
To estimate home addition costs, determine your addition type, desired square footage, foundation needs and finish quality level. Our home addition cost calculator does this automatically based on your selections. As a rule of thumb, budget $150 to $350 per square foot for most additions, with bathrooms and kitchens at the higher end due to plumbing requirements.
What is the cost of a home addition calculator estimate per square foot?
Home addition cost per square foot ranges from $80 for a basic garage to $600 for a luxury bathroom or kitchen addition. Most residential additions fall between $150 and $350 per square foot. Second story additions typically run $200 to $500 per square foot due to structural complexity.
Does a home addition increase property taxes?
Yes. Adding square footage increases your home's assessed value, which typically increases property taxes. Expect assessed value to increase by 70-90% of the addition's construction cost. At a 1.2% effective tax rate, a $100000 addition increases annual property taxes by approximately $840 to $1080 per year.
What percentage of home addition cost is recouped at resale?
According to industry data, a well-planned home addition can recoup up to 70-80% of its cost at resale. The type and quality of the addition, along with overall home condition and local market, play significant roles. Bedrooms and bathrooms tend to have the strongest return because they directly affect a home's bedroom and bathroom count.
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Disclaimer: All home addition cost estimates are for informational purposes only based on average 2026 US contractor rates. Actual costs vary significantly based on design complexity, structural requirements, local permit requirements, site conditions and contractor availability. Always obtain multiple quotes from licensed general contractors before proceeding with any construction project.