Home Addition Calculator
Estimate total costs for a new room or house expansion.
Explore tool →✦ No signup. No vague promises.Home Addition Cost Calculator
Home Addition Cost Calculator
& Planning Guide for 2026.
Explore what your home addition could cost before calling a contractor. Transparent U.S. planning scenarios, editable assumptions, and tools that help you compare real proposals.
Make decisions withclearer numbers ↗
Quick Estimate · Updated October 2026
How much could your home addition cost?
Three quick answers. An instant, itemized U.S. planning estimate. No account, phone number, or email required.
Free and instantEasy to customizePrivate in your browser
YOUR PROJECT
Start with the basics
Get an estimate in under a minute. You can refine the details anytime.
Your planning estimate
Project snapshot
Choose your project to see a low-to-high budget breakdown.
Planning example, not a binding quote. Your actual costs depend on local labor, permits, site access and design. We do not use live ZIP-code prices. Confirm details with local permit officials and request itemized quotes from licensed, insured contractors. How the estimate works →
8 useful toolsNot just generic articles
Line-by-lineVisible planning allowances
100% browser-sideNo account or lead form
Know your starting point
Home addition cost per square foot (2026)
Published national guides describe broad construction ranges; different room types, site conditions, and scopes are not directly interchangeable. These are the illustrative standard-finish assumptions inside the tool above, before local or state scenario adjustments.
| Type of addition | Construction planning band | Adjust assumptions |
|---|---|---|
| Bedroom / living space | $120–$250 | Model costs → |
| Bathroom addition | $200–$425 | Model costs → |
| Kitchen extension | $220–$450 | Model costs → |
| Sunroom | $100–$325 | Model costs → |
| Attached garage | $85–$185 | Model costs → |
| Second story | $200–$500 | Model costs → |
| Detached ADU | $180–$350 | Model costs → |
The table is NOT a price list for your city. Compare national context from Angi’s 2026 cost guide and HomeGuide, then use our formula notes and request local bids.
Tools that do the math
A plan for every kind of extra space.
From a new bedroom to an ADU: see scenario costs, understand add-ons, and take the numbers to a contractor.
Room Cost Calculator
Compare bedroom, kitchen, bathroom and sunroom budgets.
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Second Story Calculator
Understand building up, stairways and structural upgrades.
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ADU & Guest House Calculator
Model construction costs and a conservative rental scenario.
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Resale ROI Calculator
Estimate the portion of cost potentially recovered at resale.
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Loan Payments Calculator
Plan illustrative monthly principal-and-interest payments.
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Compare Contractor Bids Calculator
Spot exclusions and compare two proposals side by side.
Explore tool →Permit & Soft Cost Calculator
Plan design, engineering, permit and contingency allowances transparently.
Explore tool →Card images are AI-generated design concepts, not photographs of completed construction projects.
Plan by location
Start with your state, then check local rules.
These guides explain common permitting and site questions. They use clearly labeled planning scenarios—not contractor prices for your ZIP code.
Make a smarter call
A better estimate is one you can actually explain.
01
Describe your space
Choose the project, square footage and finish level—not your phone number.
02
See the whole budget
View construction, optional work, planning fees and a contingency allowance.
03
Compare local quotes
Use our worksheet to spot excluded items and ask better questions.
Practical learning
From rough idea to real bids.
Start with the questions homeowners actually search before calling contractors.
Cost guide
How Much Does a Home Addition Cost in 2026?
Project budgets, square footage and the hidden costs that change the total.
Read guide →Cost guide
Home Addition Cost per Square Foot
Compare bedrooms, bathrooms, kitchens, garages, sunrooms and second stories.
Read guide →Room cost
Bedroom Addition Cost
Planning ranges and a worked 300 sq ft bedroom example.
Read guide →Room cost
Bathroom Addition Cost
Plumbing, waterproofing, fixtures and permit-driven budget questions.
Read guide →Size guide
400 Sq Ft Home Addition Cost
A worked all-in planning example with soft costs and contingency.
Read guide →Decision guide
Build Up vs. Build Out
Compare structure, lot use, disruption and second-story cost tradeoffs.
Read guide →Good to know
Common questions
What does a typical 400 sq ft room addition cost?
Published U.S. guides show a wide span depending on finish and scope. Our interactive example starts at about $58,000–$127,000 with a 15% contingency for a national standard bedroom scenario. This is an illustration, not a local quote.
Do you use real ZIP code labor rates?
No. State and local price factors are openly labeled editorial what-if scenarios, not purchased datasets or contractor bid averages. Compare local written quotes for actual pricing.
Does the estimate include a standard foundation?
The base room scenario includes ordinary construction and a normal foundation. If you need a crawl space, basement, or difficult excavation, add the separate incremental allowance. Ask your engineer and contractor to confirm scope.
Can I include extra bathroom, HVAC or wiring work?
Yes. Select optional line items to add explicit budget allowances. Bathroom and kitchen base categories already contain normal plumbing; avoid double-counting the same work.
What should I put in contingency?
15% is the example default. Your appropriate allowance depends on the age of the building, hidden conditions, design completion, local site and risk. An early design may need more.
Are design fees and building permits included?
A broad 5–10% planning allowance is added separately. It does not represent your actual city permit fee or professional quote.
Can I export or share my estimate?
You can export a CSV worksheet, use your browser to print/save a PDF, or copy a URL containing your chosen assumptions. Sharing that URL reveals the non-personal project values in it.
Do I have to give my name or phone number?
No. All calculator inputs stay in your browser. We currently do not sell lead lists or run a contractor-matching form.
Start with a budget you understand.
Our tools are free to use; you decide when to contact a professional.