How to calculate square footage for tile
Tile square footage is the total surface area you plan to cover, measured in square feet. It's the number every tile job starts with, because tile is sold by the box and priced by the square foot. The math is straightforward — length times width for each surface — but the details decide whether you finish the job or run out one row short. Start by measuring each floor or wall in feet, multiply length by width, and add the pieces together for your total area.
For a rectangular room, one measurement of length and width is all you need. For irregular spaces, break the room into clean rectangles, calculate each one, and sum them. The same method you'd use for a flooring estimate applies here — the calculator above does the multiplication and the waste factor for you once you enter your dimensions.
Why you add a waste factor and buy extra
You never order exactly the area you measured. Tiles get cut to fit against walls and around corners, some crack during installation, and a diagonal or herringbone layout wastes far more at the edges than a straight grid. Professionals add 10% to the measured area for a standard layout and 15% for diagonal, herringbone, or rooms with lots of cuts. That overage is built into the tool so your box count is realistic.
Buy a little beyond the waste factor too, and set the spares aside. Tile is made in dye lots, and a box bought two years later rarely matches the original color exactly. Keeping four or five tiles from the same lot means a cracked tile becomes a five-minute repair instead of a whole new floor. If you're pricing the job, feed your total into the cost calculator with your price per square foot.
Floor tile vs. wall tile — measure them separately
Floors and walls almost always use different tile in different sizes, so measure and order them as separate line items. Floor tile is measured as length times width of the room; wall tile is measured as the run length times the height you're tiling. A countertop backsplash, a shower surround, and the shower floor are each their own calculation with their own box coverage.
Because coverage per box depends on tile size — a box of large-format 12×24 tiles covers more area than a box of small mosaics — always divide by the coverage printed on the box you're actually buying, not a generic number. Round every surface up to whole boxes on its own, then total the boxes at the end.