Bathroom Tile Calculator

Buying tile by eye is how most overage and shortage problems start. Order too little and your second box may come from a different production lot with a visible shade shift; order too much and the leftover sits in a garage. The bathroom tile calculator above solves that by combining your room's area, tile size, and layout pattern into a single tile, box, and grout order — with a live preview so you can see the pattern before you commit to it.

Below, we explain how the tile and waste math works, why the layout pattern changes how much extra to buy, how grout quantity is actually calculated, and the code and waterproofing details that matter specifically in a bathroom.

How to use the calculator

1. Choose whether the tile is going on a floor, wall, or in a shower / wet area.
2. Enter the room's length and width, and subtract any fixture footprint (vanity, tub) that won't be tiled.
3. Pick a tile size from the presets or enter a custom size, plus tile thickness.
4. Choose a layout pattern — straight, running bond, diagonal, or herringbone — and watch the preview update.
5. Set your grout joint width, grout type, and the coverage per box printed on your tile's packaging.
6. Read off boxes to buy, approximate tile count, and the grout bags needed.

Why the layout pattern changes how much tile to buy

Every layout pattern wastes a different amount of tile to cuts, and that waste has to be bought as extra material up front:

Pattern	Typical waste	Why
Straight / grid	10%	Cuts only at room edges
Running bond (offset)	12%	Half-tile cuts at the start/end of alternating rows
Diagonal (45°)	15%	Triangular cuts along every wall
Herringbone	18%	Angled cuts at every border, plus tighter piece-to-piece tolerances

Large-format tile (2 square feet or more per piece — think 24×24 inch or bigger) adds roughly another 5% on top of the pattern's base waste, since fewer, bigger cuts still consume a whole tile. Buy your waste allowance in the same order as the field tile so every box matches the same production lot; ordering a top-up later risks a visible shade or texture difference.

How the grout estimate works

Grout quantity is a volume problem, not a simple per-square-foot number: it depends on how much joint length there is per square foot (smaller tile = more joints = more grout), how wide the joint is, and how thick the tile is (which sets joint depth). The calculator estimates grout weight from those three inputs times a typical grout density, then converts to bags:

• Smaller tile (subway, mosaic) has far more joint length per square foot than large-format tile, so it needs proportionally more grout.
• A 1/4-inch joint holds roughly four times the grout of a 1/16-inch joint for the same tile.
• Sanded grout is used for joints from about 1/8 to 1/2 inch; unsanded for joints under 1/8 inch; epoxy works across both but costs more and resists moisture better.

Because bag coverage varies by manufacturer and product line, treat the calculator's bag count as a solid estimate and confirm against the specific product's coverage chart before checkout — buying one extra small bag is far cheaper than a second trip mid-project.

Wet areas need more than just the right grout

Showers and other wet areas carry extra requirements beyond tile and grout selection. A waterproofing membrane behind the tile is typically rated for around 40 square feet of coverage per gallon, per coat, and most manufacturers require two coats for a full waterproof rating. Shower floors also need a minimum slope to the drain — commonly 1/4 inch of fall per foot under the International Plumbing Code — built into the mortar bed before tile ever goes down. None of this shows up in a tile count, but skipping it is the most common cause of a shower that looks finished and fails within a year.

Common bathroom tiling mistakes

• Ordering the exact square footage with no waste allowance, then running short mid-installation.
• Mixing dye lots because a top-up order shipped from different production runs than the original.
• Using cement-based grout in a shower instead of epoxy, where moisture exposure is constant.
• Choosing herringbone or diagonal without budgeting the extra waste those patterns require.
• Skipping the waterproofing membrane or slope-to-drain on a shower floor because it isn't visible once tiled.

Frequently asked questions

How many tiles do I need for a bathroom floor? 

Multiply the room's length by width to get square footage, subtract any fixture footprint, divide by the tile's square footage, then add your pattern's waste percentage — 10% for a straight layout is typical. The calculator above does this automatically for any tile size.

How much extra tile should I buy? 

At minimum, buy your pattern's waste allowance (10–18% depending on layout) on top of the exact square footage, and always round up to the next full box so replacement tile comes from the same dye lot if you ever need a repair.

Do I need epoxy grout for a shower? 

It's not mandatory, but epoxy resists moisture and mildew better than cement-based sanded or unsanded grout, which is why it's the more common recommendation for shower floors and walls specifically.

Does tile size affect how much grout I need? 

Yes — smaller tiles have far more grout joint per square foot than large-format tiles, so a mosaic or subway tile project needs noticeably more grout than the same area in 24×24 inch tile.

Why does herringbone need more tile than a straight layout? 

Herringbone requires angled cuts along every border of the room, and the interlocking layout leaves less usable material per cut piece, which is why it typically carries a higher waste allowance than a straight or offset pattern.