Adding a bathroom costs $5,000 to $25,000 when you convert existing space, or $20,000 to $75,000 when you build a new addition.2 National averages land at $20,000 to $35,000 (Fixr, Angi).13 Prices below are national averages* for 2026.
*National averages, not local quotes. Your price depends on bathroom type (half, three-quarter, full, primary), whether plumbing already exists nearby, and finish level. Electrical work, permits, and structural changes add $550 to $14,500 (Angi).1
$20,000
average, Fixr
$200 – $250
per sq ft conversion, HomeGuide
$400 – $550
per sq ft addition, Angi / HomeGuide
$35,000
average, Angi
Quick math: a 50-sq-ft basement conversion at HomeGuide’s $200 to $250 per square foot = $10,000 to $12,500, inside its $10,000–$25,000 basement range, our arithmetic.2 The national averages disagree ($20,000 at Fixr, $35,000 at Angi) because Angi blends in primary and Jack-and-Jill builds that reach $100,000, our reading.13
Conversion vs addition: the big fork
| Project | Per sq ft | Total | Source |
|---|---|---|---|
| Convert existing space | $200 – $250 | $5,000 – $25,000 | HomeGuide |
| Build new addition | $400 – $550 | $20,000 – $75,000 | HomeGuide / Angi |
Conversions cost roughly half of additions per foot because the walls, floor, and roof already exist — you are paying for plumbing, electrical, and finishes, not structure, our reading.2
Cost by bathroom type (Angi)
| Type | Cost | Fixtures |
|---|---|---|
| Half bath | $4,000 – $12,000 | Toilet + sink |
| Three-quarter | $6,000 – $22,000 | Adds shower |
| Full | $10,000 – $50,000 | Adds tub or tub-shower |
| Primary | $22,000 – $90,000 | Double vanity, separate shower/tub |
| Jack and Jill | $25,000 – $100,000 | Shared between two bedrooms |
| Wet room | $6,000 – $20,000 | Waterproofed open shower space |
Fixture count drives cost more than square footage: every added fixture is another supply line, drain, and vent run, our synthesis of the Angi table.1
Where the space comes from (HomeGuide conversions)
| Space | Size (sq ft) | Cost |
|---|---|---|
| Closet / under staircase | 15 – 30 | $3,000 – $7,500 |
| Laundry room | 40 – 70 | $7,500 – $16,000 |
| Upstairs space | 40 – 80 | $8,000 – $20,000 |
| Basement | 50 – 100 | $10,000 – $25,000 |
Closet and under-stair conversions are the cheapest way to add a half bath; basements cost more because the drainage often needs an up-flush or sewage-ejector pump, our reading.2
Budget for the extras
Permits, electrical, and structural modifications add $550 to $14,500 depending on scope (Angi). An addition that extends the foundation sits at the top of that range; a closet conversion with existing electrical nearby sits at the bottom.1
Related guides
Second Story Addition Cost (2026 Guide)
Bathroom Remodel Cost
Home Addition Cost
Basement Finishing Cost
All cost guides
Sources
1. Angi — How Much Does It Cost to Add a Bathroom?
2. HomeGuide — Cost to Add a Bathroom
3. Fixr — Bathroom Addition Cost