Calculate bathroom area, tile quantity, and trim pieces from room dimensions, exclusions, waste factors, and tile or trim sizes.

Bathroom Area Calculator

Enter measurements and click Calculate.

Bathroom Area
Tile Quantity
Trim Pieces
Bathroom floor or wall areas
Area
Length ft
Length in
Width/Height ft
Width/Height in
Area 1
Area 2
Area 3
Area 4
Tile estimate
Bullnose, liner, or exposed-edge trim
Run
Length ft
Length in
Extra ft
Extra in
Run 1
Run 2
Run 3
Show Calculation Steps ▼

Related Calculators

Bathroom Area Formula

The calculator uses square feet as the main working unit. Feet and inches are combined before each area, tile, or trim calculation.

L = LF + LI/12
W = WF + WI/12
A_i = L_i * W_i
A_{measured} = A_1 + A_2 + A_3 + A_4
A_{net} = A_{measured} - A_{excluded}
A_{recommended} = A_{net} * (1 + Waste/100)
  • L = length in feet
  • W = width or height in feet
  • LF = length feet entered
  • LI = length inches entered
  • WF = width or height feet entered
  • WI = width or height inches entered
  • A_i = area of one measured section in square feet
  • A measured = total measured bathroom area before exclusions
  • A excluded = tub, vanity, opening, or other area not being covered
  • A net = area after exclusions
  • Waste = extra percentage added for cuts, breakage, and layout adjustments

For the bathroom area tab, each rectangular floor or wall section is calculated separately, then added together. Any excluded area is subtracted, then the waste factor is applied to give the recommended amount to buy or cover.

EL = TL + G
EW = TW + G
C_{tile} = EL * EW
Tiles_{base} = A_{cover} / C_{tile}
Tiles_{needed} = ceil(Tiles_{base} * (1 + (PatternWaste + ExtraWaste)/100))
Boxes = ceil(Tiles_{needed} / TilesPerBox)
Cost = Boxes * PricePerBox
  • TL = tile length converted to feet
  • TW = tile width converted to feet
  • G = grout gap or overlap converted to feet
  • EL = effective tile length
  • EW = effective tile width
  • C tile = coverage per tile in square feet
  • A cover = area to cover in square feet
  • PatternWaste = extra percentage for the selected layout pattern
  • ExtraWaste = additional waste percentage you enter
  • ceil = round up to the next whole number

For the tile quantity tab, the calculator can use the bathroom area result or a manual total area. It divides the cover area by the effective tile coverage, adds layout and waste percentages, then rounds up to whole tiles. If tiles per box and price per box are entered, it also estimates boxes and cost.

R_i = LF_i + LI_i/12 + EF_i + EI_i/12
R_{total} = R_1 + R_2 + R_3
R_{needed} = R_{total} * (1 + Waste/100)
TrimPieces = ceil(R_{needed} / PieceLength)
  • R_i = length of one trim run in feet
  • LF_i = run length feet entered
  • LI_i = run length inches entered
  • EF_i = extra feet entered for that run
  • EI_i = extra inches entered for that run
  • R total = total trim length before waste
  • R needed = trim length after waste
  • PieceLength = length of one trim piece converted to feet

For the trim tab, each exposed-edge run is added in linear feet. The waste factor is applied, then the result is divided by the trim piece length and rounded up to whole pieces.

Typical Bathroom Tile Waste and Layout Allowances

Use these ranges when you are not sure what waste factor to enter. More cuts, small rooms, niches, diagonal layouts, and patterned tile usually need more extra material.

Use case Common waste factor Notes
Simple rectangular floor, straight layout 5% to 10% Best case with few cuts.
Typical bathroom floor or wall 10% A common starting point for most projects.
Running bond or offset layout 10% to 15% More end cuts are usually needed.
Diagonal or herringbone layout 15% to 20% More angled cuts and unusable offcuts.
Small mosaic, niche, or complex shower wall 15% to 25% Useful when many edges, corners, and cutouts are involved.

Common Tile Sizes and Approximate Coverage

Tile size Approximate coverage per tile Tiles per 100 sq ft before waste
3 in × 6 in 0.125 sq ft 800
4 in × 4 in 0.111 sq ft 900
6 in × 6 in 0.250 sq ft 400
12 in × 12 in 1.000 sq ft 100
12 in × 24 in 2.000 sq ft 50
24 in × 24 in 4.000 sq ft 25

Example Calculations

Example 1: Bathroom floor area with waste

You measure a bathroom floor that is 8 ft 6 in long and 5 ft 0 in wide. A vanity footprint of 4 sq ft will not be tiled. You want to add 10% waste.

L = 8 + 6/12 = 8.5 ft
W = 5 + 0/12 = 5 ft
A_{measured} = 8.5 * 5 = 42.5 sq ft
A_{net} = 42.5 - 4 = 38.5 sq ft
A_{recommended} = 38.5 * (1 + 10/100) = 42.35 sq ft

The recommended amount is 42.35 sq ft.

Example 2: Tile quantity and boxes

You need to cover 80 sq ft with 12 in × 24 in tile. The grout gap is 0 in for this check, layout waste is 10%, additional waste is 10%, and each box has 8 tiles.

C_{tile} = 1 ft * 2 ft = 2 sq ft
Tiles_{base} = 80 / 2 = 40
Tiles_{needed} = ceil(40 * (1 + 20/100)) = 48
Boxes = ceil(48 / 8) = 6

You need 48 tiles, or 6 boxes.

FAQ

Should you subtract the bathtub, vanity, or toilet area?

Subtract an area only if tile or flooring will not go under it. For example, subtract a built-in tub footprint if the floor tile stops at the tub. Do not subtract a toilet footprint if the tile continues under the toilet. For wall tile, subtract large openings or sections that will not receive tile.

What waste factor should you use for bathroom tile?

Use 10% for a typical straight bathroom layout. Use 15% or more for diagonal, herringbone, offset patterns, small mosaic sheets, niches, or rooms with many cuts. If the tile may be hard to match later, buying extra from the same lot can help avoid color and size differences.

Why does the tile result round up?

You cannot buy part of an individual tile or part of a box in most cases. The calculator rounds tile counts and box counts up so the estimate covers the full area after waste is added.