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What the bathroom adds
Fixr lists a new half bath at $5,000–$15,000, a three-quarter bath at $10,000–$22,000 and a full bath at $15,000–$35,000, and puts basement bathrooms specifically at $10,000–$60,000 depending on how far the drain has to travel. HomeGuide's estimate for converting existing basement space runs $200–$250 per square foot of bathroom, or $3,000–$12,500 for 15 to 50 sq ft.
| Basement size | Mid-range finish | With half bath | With full bath |
|---|---|---|---|
| 600 sq ft | $24,000–$45,000 | $29,000–$60,000 | $39,000–$80,000 |
| 800 sq ft | $32,000–$60,000 | $37,000–$75,000 | $47,000–$95,000 |
| 1,000 sq ft | $40,000–$75,000 | $45,000–$90,000 | $55,000–$110,000 |
| 1,200 sq ft | $48,000–$90,000 | $53,000–$105,000 | $63,000–$125,000 |
| 1,500 sq ft | $60,000–$112,500 | $65,000–$127,500 | $75,000–$147,500 |
How this estimate is built
The base number is area times a published cost per square foot. Block Renovation, a remodeling contractor, puts contractor-led basement finishes at $25–$40 per square foot for a basic finish, $40–$75 for mid-range and $75–$100 or more for high-end work in 2026. HomeAdvisor's national figure is lower, $7–$23 per square foot, because it also counts partly finished spaces and owner-managed projects. Use the HomeAdvisor range if you will act as your own general contractor or only need flooring, paint and lighting in an already dry, framed room.
Add-ons are priced separately because they do not scale with area. A bathroom costs about the same whether it sits in a 600 or a 1,600 square foot basement. Fixr lists half baths at $5,000–$15,000, three-quarter baths at $10,000–$22,000 and full baths at $15,000–$35,000. HomeGuide puts a cut-in egress window at $4,000–$12,000, most often $6,000–$8,000. HomeAdvisor lists permits at $1,200–$2,000.
When you pick a state, the calculator keeps 60% of the cost as is and scales the other 40% by local wages. This Old House notes that labor is usually about 40% of a basement finishing budget, and the wage index comes from the Bureau of Labor Statistics' May 2025 mean hourly wages for carpenters, electricians, plumbers and drywall installers.
Add-on prices
| Add-on | Low | High |
|---|---|---|
| Half bath | $5,000 | $15,000 |
| Three-quarter bath | $10,000 | $22,000 |
| Full bath | $15,000 | $35,000 |
| Egress window, each | $4,000 | $12,000 |
| Building permit | $1,200 | $2,000 |
Bathroom ranges from Fixr; egress from HomeGuide; permits from HomeAdvisor.
What moves the price
- Water. A basement that leaks must be fixed first. HomeAdvisor's average waterproofing job is $4,400, and none of that shows up in a per-square-foot finishing price.
- Plumbing. Adding a toilet below the sewer line needs an ejector pit or upflush system. Rough-in pipes left by the builder cut the cost of a bathroom sharply.
- Ceiling height. Ducts and beams that hang below 6′ 4″ have to be moved, or the floor lowered, before a room can count as habitable.
- Bedrooms. Every sleeping room in a basement needs its own emergency escape opening under IRC R310, so each bedroom can add an egress window.
- Finish choices. Block Renovation lists luxury vinyl plank at $3–$7 per sq ft installed, carpet at $2–$5 and ceramic tile at $5–$10.
The usual order of work
| Phase | Who | Notes |
|---|---|---|
| 1. Water and radon | Waterproofer, mitigator | Test radon and fix leaks before anything is covered |
| 2. Permit and plan | Owner, designer | Rooms, egress windows, bathroom location |
| 3. Egress and drains | Excavator, plumber | Cut windows and break slab for drains while the space is open |
| 4. Framing and insulation | Carpenter | Foam on the concrete, treated bottom plates, fire blocking |
| 5. Rough electrical, plumbing, HVAC | Licensed trades | Inspections before walls close |
| 6. Drywall and ceiling | Drywall crew | Leave access panels for valves and cleanouts |
| 7. Flooring, trim, paint, fixtures | Finish trades or owner | Final inspection |
Bathroom and egress costs land early, in phase 3, which is why they surprise people who budget only by the square foot.
Common questions
How much does a basement bathroom add?
Half bath $5,000–$15,000, full bath $15,000–$35,000 (Fixr). Below-sewer toilets need an ejector or upflush system.
Related calculators
Sources
- https://www.blockrenovation.com/guides/basement-remodel-cost-per-square-foot-2026
- https://www.homeadvisor.com/cost/basements/
- https://www.thisoldhouse.com/foundations/reviews/cost-to-finish-basement
- https://www.fixr.com/costs/bathroom-addition
- https://homeguide.com/costs/egress-window-installation-cost
- https://api.bls.gov/publicAPI/v1/timeseries/data/ (OEWS series OEUS…472031, 472111, 472152, 472081, May 2025)
- https://homeguide.com/costs/cost-to-put-bathroom-in-basement