Bathroom Tile Calculator
Calculate how many tiles you need for a bathroom floor, walls, or both — with waste included for cuts around fixtures and fittings.
How to Use This Calculator
For the bathroom floor, enter the room length and width in feet. Select your tile size using the quick-pick buttons (12×12 is the most common bathroom floor tile) or enter a custom size. Choose 10% waste for a straight-lay floor, 15% for a diagonal pattern or a floor with a lot of cut-ins around the toilet and vanity. For bathroom walls, run the calculator separately using the wall area (length × height of each wall section) and add the tile totals together. Enter tiles per box and price per box from your product label to get cost and box count.
How to Calculate Bathroom Tile
Tile count formula: tiles = ⌈(area in sq ft × (1 + waste%÷100)) ÷ tile area in sq ft⌉. Convert tile dimensions from inches to square feet by multiplying width × length ÷ 144. For a 12×12 tile: 12 × 12 ÷ 144 = 1.00 sq ft per tile. For an 18×18 tile: 18 × 18 ÷ 144 = 2.25 sq ft per tile.
Bathroom floor example: a 6 × 9 bathroom (54 sq ft) with 12×24 tile and 10% waste. Area with waste = 54 × 1.10 = 59.4 sq ft. Tile area = 12 × 24 ÷ 144 = 2.0 sq ft. Tiles needed = 59.4 ÷ 2.0 = 29.7 — order 30 tiles. If your box contains 8 tiles (16 sq ft per box), that is 4 boxes.
For cut-ins around the toilet and pedestal sink, add an additional 5% beyond your standard waste factor. These cuts are often diagonal or curved and cannot be reused, making them pure waste. The 15% waste setting in the calculator accounts for this when working in a typical bathroom with fixtures.
Bathroom Tile Tips
Locate the center of the room before laying out any tile. Snap chalk lines from the center of each wall to find the exact room center, then dry-lay your first row of tiles from the center outward toward each wall. This ensures cut tiles at each wall are equal in size — a balanced layout looks professional; a random assortment of skinny cut tiles at one wall looks like an afterthought.
Use a waterproofing membrane in wet areas. The tile itself is waterproof, but the grout and substrate are not. In shower surrounds, around the tub deck, and anywhere water pooling is possible, apply a sheet or liquid waterproofing membrane to the substrate before tiling. Kerdi, RedGard, or similar products prevent water from reaching the subfloor and causing rot, mold, and tile delamination.
Check that floor tile is rated slip-resistant for wet use. Look for a COF (coefficient of friction) rating of 0.50 or above for floor tiles. Polished or glazed tiles are beautiful on walls but dangerously slippery when wet on a floor. Honed, matte, or textured finishes provide the traction needed in a bathroom environment.
What to Buy
For bathroom floors, MSI Tile and Daltile offer broad selections of porcelain floor tile with explicit COF ratings and PEI ratings listed on their product pages. Porcelain (water absorption under 0.5%) outperforms ceramic in wet environments — look for "porcelain" in the product description, not just "tile."
For setting materials, use Laticrete 254 Platinum thinset for porcelain tiles — it provides the bond strength and flexibility needed in wet areas. For grout, Laticrete SpectraLOCK or TEC Power Grout are epoxy-based options that resist staining and mold without the brittleness of standard cement grout. These products cost more upfront but eliminate the need for annual resealing.
Frequently Asked Questions
How many tiles do I need for a 5×8 bathroom floor? +
A 5 × 8 bathroom is 40 square feet. With a 10% waste factor, you need 44 sq ft of tile. For 12×12 tiles (1 sq ft each), that is 44 tiles. For 18×18 tiles (2.25 sq ft each), that is 20 tiles. Always use the calculator with your specific tile size — tile dimensions in inches are listed on the box and vary widely between products.
What size tile is best for a small bathroom? +
Contrary to old advice, larger tiles work well in small bathrooms — fewer grout lines make the space feel less busy and appear larger. A 12×24 or 18×18 tile is a good choice for bathrooms under 50 sq ft. For very small floors under 25 sq ft, mosaic sheets (2×2 or smaller tiles on mesh backing) provide better slip resistance and scale well to the space. Avoid floor tiles larger than 24 inches in bathrooms — the limited cutting room around the toilet and vanity creates excessive waste.
What PEI rating do I need for bathroom floor tile? +
PEI 3 is the minimum for residential bathroom floors that see daily foot traffic. PEI 4 is recommended for bathrooms used by multiple people or in master baths with heavy daily use. Wall tiles do not need a PEI rating since they carry no foot traffic — any tile rated PEI 0 or above is suitable for bathroom walls. Never use a wall-only tile on the floor.
How much extra tile should I buy for a bathroom? +
Buy 10% extra for a rectangular bathroom with a straight-lay pattern. Buy 15% extra if there are multiple cut-ins around the toilet base, pedestal sink, or tub surround. Buy 15 to 20% extra for diagonal or herringbone patterns. Always buy at least one full box extra — bathrooms are one of the most likely rooms to need future tile replacement due to cracking, grout failure, or plumbing repairs, and matching tile from the same lot becomes impossible once a line is discontinued.
Do I need different tiles for the bathroom floor and walls? +
Yes, in most cases. Floor tile must be rated for floor use (PEI 3+) and ideally have a slip-resistant texture or finish. Wall tile can be smoother, lighter, and more decorative — it does not need a PEI rating. Many homeowners use the same tile for both surfaces for a clean, continuous look, as long as the chosen tile has the appropriate floor rating. Glossy wall tiles are not suitable for floors due to slip risk when wet.
What grout should I use in a bathroom? +
Unsanded grout for joints under 1/8 inch. Sanded grout for joints 1/8 inch and wider. In wet areas around the tub and shower, use epoxy grout or a polymer-modified grout — these resist mold and moisture penetration better than standard cement grout. Seal all cement-based grout with a penetrating sealer within 72 hours of installation and reseal annually in shower areas. Light-colored grout in bathrooms stains easily — consider medium or dark tones for lower maintenance.
Can I tile over existing bathroom tile? +
Yes, if the existing tile is firmly bonded, flat, and the added height won't cause problems with door clearance, toilet flange height, or transitions to adjacent flooring. Use a floor-leveling compound to fill grout lines before setting new tile over old tile — this prevents "print through" where the new tile telegraphs the grid of the old tile below. Check that the combined tile weight does not exceed your subfloor's load capacity.
