How to Calculate How Many Tiles You Need
I built this tile calculator to give you an accurate tile count before you head to the tile shop. Tiles are typically sold by the box (a set number of square feet per box), and getting the count right matters because tile colours vary between batches. If you run out mid-project and the store is out of your batch, you may end up with a visible colour mismatch that's visible every time you walk in the room. Always order from one batch, and order enough.
The calculation divides the total area to be tiled by the area of a single tile, then adjusts for grout joint width (which reduces the effective area of each tile slightly) and adds a waste factor. For a simple rectangular floor, multiply length × width to get the area. For wall tiles, measure each wall section separately and add them together. Subtract any areas that won't be tiled (large appliances, fixed cabinetry).
Waste Percentages by Layout Pattern
Tile waste comes from cuts at walls, corners, and obstacles. The more complex the layout, the more cuts you make and the more waste you generate. Here are typical waste allowances:
- Straight lay (tiles parallel to walls): 10% waste for most rooms.
- Offset (brick) pattern: 10–12% waste — the staggered joints cause longer cuts at the perimeter.
- Diagonal (45-degree) layout: 15–20% waste; much more cut material at every wall edge.
- Herringbone pattern: 20–25% waste; every cut is angled and very little offcut can be reused.
Choosing Tile Size and Grout Joint Width
Larger format tiles (12" × 24", 24" × 24", and bigger) are the dominant trend in modern bathrooms and kitchens. They make rooms look larger, have fewer grout lines to clean, and can be installed faster per square foot. The trade-off is that large format tiles require a very flat, rigid subfloor — any deflection or high spots will cause lippage (uneven tile edges) or cracking. Use self-leveling compound to flatten subfloors before installing large tiles.
Grout joint width affects both the look and the function of a tile installation. Rectified tiles (ground to precise dimensions) can be laid with joints as narrow as 1/16". Standard tiles work best with 1/8" to 3/16" joints. Floor tiles generally use wider joints (3/16" to 1/4") because wider grout lines provide more grip. Unsanded grout is used for joints under 1/8"; sanded grout is required for larger joints because it resists shrinkage and cracking.
Frequently Asked Questions
How much thinset mortar do I need for tiling?
A 50 lb bag of thinset mortar typically covers 40–50 square feet at 3/16" coverage depth (standard floor tile). Coverage varies based on tile size and back-buttering technique. For large format tiles (over 15"), use a large-notch trowel and back-butter tiles to ensure 95% coverage — insufficient coverage under large tiles causes cracking. Plan on approximately one bag of thinset per 40 square feet as a safe starting estimate.
What is the difference between floor tile and wall tile?
Floor tiles are rated for foot traffic and slip resistance (look for a Coefficient of Friction rating above 0.6 for wet areas). Wall tiles are typically lighter, thinner, and have a glossier surface finish that makes them easier to clean but unsuitable for floors. You can usually use floor tiles on walls, but you should never use wall-rated tile on a floor — it won't hold up under foot traffic and can be a slip hazard in wet areas.
Do I need to seal tile grout?
Yes, for most grout types. Cement-based sanded and unsanded grout is porous and will stain easily if unsealed — particularly in kitchen backsplashes and bathroom shower floors. Apply a penetrating grout sealer 48–72 hours after grouting, once the grout has fully cured. Reapply sealer every 1–2 years depending on use. Epoxy grout does not require sealing and is an excellent choice for wet areas like showers, though it's harder to work with and more expensive.
