About Home Addition Cost Calculator
We built this tool because every online calculator we tried gave us the same vague answer: "It depends." That's not useful when you're trying to decide whether to build or move.
Why we built this
Most homeowners start researching home addition costs with a simple question: "What will this actually cost me?" What they find are either impossibly vague ranges ($20,000 to $200,000 for a bedroom addition) or contractor quote forms that immediately funnel them into a sales process before they're ready.
We wanted something in between. A tool that gives you a real planning number based on your specific project, your location, and your quality expectations — without requiring you to talk to anyone first.
The calculator uses the same cost data professional estimators use: RS Means Building Construction Cost Data, NAHB survey figures, and BLS Producer Price Index adjustments. We apply regional multipliers for seven US cost zones and quality multipliers for four finish tiers. The result is a range, not a false-precision single number, because that's what honest estimating looks like.
What makes our data trustworthy
Real data sources
Our base costs come from RS Means Building Construction Cost Data and the NAHB Cost of Constructing a Home survey. These are the same sources professional estimators use.
Quarterly updates
We update every cost figure in January, April, July, and October using the Bureau of Labor Statistics Producer Price Index. Stale data is worse than no data.
No hidden agenda
We don't sell contractor leads or referral fees. The calculator is free because we run display ads. That's it. Your estimate isn't influenced by who paid us.
Transparent methodology
Every formula is documented on our How We Calculate page. You can see exactly how your ZIP, addition type, and quality tier combine to produce your estimate.
What this tool is not
- ✕A substitute for contractor quotes. Always get at least three before committing.
- ✕A structural or engineering assessment. Your project needs a professional site visit.
- ✕A permit guide. Permit requirements vary by municipality and change frequently.
- ✕A guarantee. Construction costs are estimates by nature — materials and labor fluctuate.
Questions about our methodology?