Cost Estimators

Home Addition & Construction Cost Calculator

This home addition cost calculator frames a budget by square foot for additions and renovations; our home addition guide covers types and permits. Use per-square-foot ranges to frame the budget for a room addition or a whole-house renovation. Defaults: additions $120–$300 per sq ft (2026 national range around a $185 average); renovations $15–$150 per sq ft from cosmetic updates to premium whole-house work. Add design, engineering and permit costs as a percentage.

Results from this calculator are planning estimates; confirm quantities and prices with your supplier or contractor before you order.

Your results will appear here

Enter your measurements and press Calculate. Defaults show a typical example.

How to use the home addition / construction cost calculator

Choose addition or renovation.
Enter the square footage.
Set a local cost factor and soft-cost percentage.
Override the rates with local bids when available.

Formula

Total = area × cost per sq ft × local factor × (1 + soft-cost %).

Worked example

A 400 sq ft addition at $120–$300 per sq ft plus 10% soft costs: $52,800–$132,000.

Tips for using the home addition / construction cost calculator

Kitchens and bathrooms in an addition raise the cost per square foot the most.
Budget soft costs such as design, engineering and permits on top of construction.
Foundation work and connecting to existing systems vary most from site to site.
Check zoning setbacks, height limits and lot coverage before you design; a plan that needs a variance adds months and fees that a simple per-square-foot range does not show.