Bathroom Addition Cost Calculator
Estimate the cost to add a new bathroom.
Last updated: November 5, 2026
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 project cost
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- Low-range estimate: —
- High-range estimate: —
- Typical variable cost: —
- Total excluding base fixed charges: —
On this page
Quick summary: Estimate the cost to add a new bathroom.
Read the method, example and limitations
Updated reference sections in this guide are in English.
Guide language: English. Updated October 15, 2026.
What this calculator estimates
Estimate the cost to add a new bathroom.
Inputs and units
Enter Number of bathrooms added, Low cost per bathroom ($), Typical cost per bathroom ($), High cost per bathroom ($), Design and utility connection costs ($), Contingency (%). Use the units shown. Required fields cannot be blank. Use zero only where that field and the model allow it. Select Calculate after changing the values.
Method and assumptions
For Bathroom Addition Cost Calculator, use 'Number of bathrooms added' as quantity q and 'Design and utility connection costs ($)' as the fixed charge F. For each low, typical or high unit cost U, total = (q x U + F) x (1 + contingency/100). Low must not exceed typical, and typical must not exceed high. The final breakdown labelled total excluding fixed charges includes any contingency attached to those charges.
Worked example
These are hypothetical example inputs, not a statement of local market prices.
| Number of bathrooms added | 1 |
|---|---|
| Low cost per bathroom ($) | 30000 |
| Typical cost per bathroom ($) | 55000 |
| High cost per bathroom ($) | 90000 |
| Design and utility connection costs ($) | 3000 |
| Contingency (%) | 15 |
| Low scenario | $37,950.00 |
|---|---|
| Typical scenario | $66,700.00 |
| High scenario | $106,950.00 |
| Typical variable cost | $55,000.00 |
| Total excluding base fixed charges | $63,700.00 |
Limitations
Prefilled prices for bathroom addition cost are illustrative budgeting assumptions. Replace them with local written quotes and avoid including 'Design and utility connection costs ($)' both in a unit quote and again as a fixed charge. A linear unit-cost model does not capture every scope, access, size, materials or regulatory requirement.
Match the quantity to the quoted scope
Count complete added bathrooms, not individual fixtures. Confirm whether the per-bathroom quote includes new drains, water supply and ventilation before adding the separate utility allowance.
For each low, typical or high unit rate, the calculation is (quantity × rate + fixed work) × (1 + contingency/100). The typical result uses the entered typical rate; it is not the midpoint unless you enter a midpoint rate. These three rates are your scenarios, not a market-price database. All three receive the same fixed work and percentage allowance.