Calculator
Bathroom Addition Cost Calculator
Price a full or half bathroom by size and finish. Plumbing distance and waterproofing matter as much as size, so place the bathroom near existing plumbing where the plan allows.
Cost per square foot by addition type and finish
| Addition type | Economy | Standard | Premium |
|---|---|---|---|
| Room / Bedroom | $80–$130 | $130–$200 | $200–$350 |
| Kitchen Extension | $150–$220 | $220–$350 | $350–$500 |
| Bathroom | $200–$250 | $250–$350 | $350–$500 |
| Sunroom | $100–$150 | $150–$225 | $225–$350 |
| Second Story | $200–$300 | $300–$450 | $450–$600 |
| Attached Garage | $50–$80 | $80–$120 | $120–$175 |
| ADU / In-Law Suite | $150–$200 | $200–$300 | $300–$450 |
Ranges are planning figures per square foot before foundation and optional features. The calculator below applies the same midpoints: for example, a Standard room addition uses $165 per square foot at the national average.
See the full guide: cost to add a bathroom and minimum bathroom dimensions with a shower.
Planning estimate only, based on 2026 cost data. It is not a quote. Get itemised bids from licensed local contractors before building, and set aside a 10–20% contingency for permits, design fees, and site surprises.