Home Addition Cost Calculator
Last updated: October 15, 2026
Estimate a home-addition project budget from square footage, construction, design, permits, utility work and contingency.
Starting figures illustrate this model. Enter your own measurements, quoted costs and applicable terms; this page does not retrieve live prices or provider rates.
Estimated home-addition project cost
—
- Base construction estimate: —
- Professional, permit and utility costs: —
- Estimated contingency: —
- Estimated cost per added square foot: —
On this page
Quick summary: Estimate a home-addition project budget from square footage, construction, design, permits, utility work and contingency.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate a home-addition project budget from square footage, construction, design, permits, utility work and contingency.
How to use it
Enter Addition size (square feet); Base construction cost per square foot ($); Architect and engineering fees ($); Permits and inspections ($); Utility, HVAC and electrical upgrades ($); Contingency (%). Select Calculate to update the results.
How the calculation works
Square footage is multiplied by the entered base construction cost, then design, permits and utility work are added. The contingency is applied to the subtotal.
Worked example: starting scenario
| Addition size (square feet) | 600 |
|---|---|
| Base construction cost per square foot ($) | 275 |
| Architect and engineering fees ($) | 18000 |
| Permits and inspections ($) | 6500 |
| Utility, HVAC and electrical upgrades ($) | 22000 |
| Contingency (%) | 12 |
| Estimated home-addition project cost | $236,880.00 |
|---|---|
| Base construction estimate | $165,000.00 |
| Professional, permit and utility costs | $46,500.00 |
| Estimated contingency | $25,380.00 |
| Estimated cost per added square foot | $394.80 |
Important limitations
Structural conditions, finishes, location, labor, demolition, foundation, weather, financing, code upgrades and contractor pricing vary.