🏗️Home Addition Cost Calculator
Pick the size and type of addition to see a realistic cost range and what drives it.
Your addition
Loading cost data…
Ballpark estimate. Real quotes vary with your home, location and materials.
Second-story additions often need the existing foundation and walls reinforced — get a structural engineer involved early.
Rather hire it out?
Compare prices from pros near you — it's free.
How it works
Each addition type has its own per-square-foot low, typical and high prices for structure (foundation, framing, roof), interior finishes and systems (electrical, plumbing, HVAC). Finish level scales interior finishes. We add permits and design, then apply your regional multiplier.
Worked example
A 300 sq ft bedroom addition, mid-range finish:
- Structure: 300 × $120 = $36,000
- Interior: 300 × $60 = $18,000
- Systems: 300 × $35 = $10,500
- Permits & design: $5,000
- Typical ≈ $69,500
Questions people ask
Often $150–$300 per sq ft for a bedroom, and more for bathrooms or second stories.
More calculators you might like
Bathroom Remodel Cost
Choose your bathroom type, size and level of finish to see a low-to-high cost range.
Kitchen Remodel Cost
Pick your kitchen size, remodel level and what you're changing to see a realistic cost range.
Square Footage Calculator
Add up rectangles, triangles and circles to get total square feet, square yards and square meters.
Email me my results
Pop in your email and keep your numbers handy at the store.
Last updated October 8, 2026. These results are friendly estimates to help you plan — always double-check before buying or making big decisions.