Why can a small bath cost as much per foot as a kitchen?

You still pay a plumber and electrician to mobilize, plus waterproofing in a tight room. Per-square-foot bands mislead on very small rooms; use extras and local bids.

Is a tub-to-shower conversion in the default range?

Sometimes, if the drain stays. If the drain moves or wet walls open, check layout and expect the high end—or a custom bid.

Does bath type change the math?

No. Powder, full, and primary are labels so you measure the real room. The multiply is still area × $/sq ft × layout factor + extras.

Where does waterproofing show up in the calculator?

It is inside the installed $/sq ft band only as a planning lump, not as a specified system. Ask bids to name the system.

What about mold I can already see?

EPA’s mold guidance is moisture control first. A finish range will not find the leak. Fix water, then remodel.

Bathroom Remodel Cost Breakdown: Plan Before Demolition

Last reviewed 2026-08-25.

A bathroom is a small room with a waterproofing job hiding under the tile. The calculator still uses area × an editable $/sq ft band because that is how many homeowners are quoted—then it labels the result as a range.

If the toilet or shower stays, you are comparing finish and fixture quality. If a drain moves, you are in a different project. The layout checkbox applies a 1.3× planning bump for that case.

Project plan: Bathroom Remodel Project Plan

Open the cost calculator

Typical Project Fit

Typical fit: Hybrid project

Typical label: Hybrid project. That describes a common mix of finish work and hired trades. It is not a safety rating for your house.

What moves the cost

Whether the toilet, shower valve, and tub drain stay. Relocation is not a fixture swap.
Waterproofing system in the shower—membrane, liner, or listed kit—plus who warrants it.
Tile area and substrate. Pretty tile on an unprepared wet wall is a teardown.
Ventilation: a ducted fan through the roof or sidewall is cheaper than a mold claim later.
Access: second-floor baths, slab-on-grade, and shared stacks change plumber hours.

What the calculator includes

Room rectangle (default 8 × 5 ft = 40 sq ft). Bath type is a reminder to measure the real room; it does not change the multiply step by itself.
Quality-tier $/sq ft defaults you can edit (mid-tier defaults are $250–$450 per sq ft).
A 1.3× multiplier when you check “move toilet, shower, or walls.”
Extras for a known glass door, heated floor, or similar line you already priced.

What the calculator may leave out

A named waterproofing specification or a leak test.
Joist or subfloor repair found after demo.
A new exhaust chase if the fan currently dumps into an attic.
Mold remediation if the ceiling below is stained—EPA’s mold pages start with moisture, not tile.

DIY-friendly parts

Painting outside the splash zone
Accessories and simple hardware

DIY with conditions

Vanity swap with the drain staying put
Wet-rated flooring on a sound subfloor
Drywall patches outside wet walls

Parts often hired out

Shower waterproofing
Plumbing relocations
New electrical in a wet room
Structural or joist repairs

Planning checklist

Measure the room. Do not use “half bath” as a substitute for feet.
Circle fixtures that will move. If any wet fixture moves, check the layout box in the calculator.
Ask each bid which waterproofing system they will install and how it is inspected.
Confirm the exhaust duct terminates outdoors.
If you will grind tile or sand old paint, read EPA lead and asbestos pages before demo.

Worked example: 8 × 5 ft full bath, mid tier, fixtures stay

Uses the bathroom calculator’s shipped mid-tier defaults. Change the money fields if your bids disagree.

Area = 8 × 5 = 40 sq ft.
Mid-tier defaults: $250–$450 per sq ft.
Layout unchecked, extras $0.
Low = 40 × 250 = $10,000. High = 40 × 450 = $18,000.
If the shower drain moves and you check layout: 40 × 250 × 1.3 = $13,000 and 40 × 450 × 1.3 = $23,400.

Same-layout planning range: $10,000–$18,000. Moved wet fixtures: $13,000–$23,400. A powder room can still sit high per foot because mobilization does not shrink with the room.

Common mistakes

Ordering tile before anyone looks at the subfloor.
Treating a tub-to-shower conversion as a keep-layout job when the drain must move.
Skipping exhaust because the window “is enough.” Windows do not replace a ducted fan in a closed-up house.
Comparing a keep-valve bid to a relocate-the-toilet bid on price alone.

Contractor quote checklist

Which waterproofing system, and is it named on the proposal?
Do the toilet and shower valve stay?
Is the fan ducted outdoors, and who patches the roof or siding?
What is excluded if the subfloor is rotten?
Who pulls any permit your department requires?

Stop signs

The proposal says “tile shower” with no membrane or liner named.
The floor bounces or smells like a past leak.
Someone plans to vent the fan into the attic.

FAQ

Why can a small bath cost as much per foot as a kitchen?: You still pay a plumber and electrician to mobilize, plus waterproofing in a tight room. Per-square-foot bands mislead on very small rooms; use extras and local bids.
Is a tub-to-shower conversion in the default range?: Sometimes, if the drain stays. If the drain moves or wet walls open, check layout and expect the high end—or a custom bid.
Does bath type change the math?: No. Powder, full, and primary are labels so you measure the real room. The multiply is still area × $/sq ft × layout factor + extras.
Where does waterproofing show up in the calculator?: It is inside the installed $/sq ft band only as a planning lump, not as a specified system. Ask bids to name the system.
What about mold I can already see?: EPA’s mold guidance is moisture control first. A finish range will not find the leak. Fix water, then remodel.

Related calculators

Related guides

Sources

Permit, inspection, and licensing requirements vary by location. Check with your local building department before work begins.