Tile a 10 by 8 ft room in 12 inch tile and you need 74 tiles once you build in a 10% waste factor. But that number moves with the room, not just its size. A bathroom floor squeezed around a toilet and a vanity eats more tile per square foot than an open kitchen of the exact same area.
One surface's total. Run the shower wall or backsplash separately if the job has more than one.
A calculator that only does square footage treats an open kitchen floor exactly like a cramped bathroom floor packed around a toilet flange, a vanity base, and a tub. Those are not the same job. Pretending otherwise is how people run short on tile. Every obstacle in a small wet room forces another cut, so the waste factor moves room by room instead of sitting at one fixed number for the whole house.
| Area type | Typical waste to plan for |
|---|---|
| Open kitchen or entry floor | 10% |
| Bathroom floor with fixtures to cut around | 12 to 15% |
| Shower walls with a niche, curb, and corners | 15 to 20% |
A bathroom remodel almost never comes down to one tile order. The floor is usually one product, the shower walls another, the vanity backsplash a third, each its own size and its own waste factor. Run each surface through this calculator on its own. Save thinset and grout for the end, once every surface is totaled, but keep the tile counts apart until you're ready to buy. Lump them together early and the shower, the surface that needs the most waste, quietly comes up short.
Back to that 10 by 8 room: 80 square feet on the nose. A 12 by 12 inch tile covers exactly 1 square foot, so the base count is 80 tiles. Add the standard 10% for a straight, open-floor layout and you round up to 88. Put that same 80 square feet in a bathroom, toilet and vanity in the way, bump the waste to 15%, and the order climbs to 92. Four extra tiles, same floor area, all because of what's sitting on top of it.
Thinset and grout track square footage, not tile count. Add them up across the whole job instead of room by room. One standard bag of thinset spreads over roughly 40 to 80 square feet, and where you land in that range depends on your trowel notch and tile size. Grout coverage swings even more with joint width. Pull the actual coverage chart off the bag and match it to your joint spacing rather than guessing at a flat number.
Measuring a floor is the easy part: length and width at the widest points, multiplied. A shower wall takes more legwork. Measure each panel on its own, since they're rarely identical, add the areas together, then subtract the niche opening if this calculator hasn't already done it for you. Round that niche down, not up. The tile that would have covered it was headed for the cutting table anyway.
Picture the average bathroom floor: small, and crowded with a toilet flange, a vanity base, a shower curb, sometimes all three within a few feet of each other. A bigger share of every tile near those fixtures ends up as offcut. A kitchen floor is usually just a bigger, plainer rectangle, so the same size tile goes further per square foot.
Yes, run it twice, or as many times as you have surfaces. Floor tile and shower wall tile are usually different sizes with different waste factors, and a shower wall brings corners, a niche, and a curb that a flat floor simply doesn't have. Calculate each surface on its own and keep the totals separate until it's time to place the order.
Give each surface its own line item on the shopping list, the floor, the shower walls, and a vanity backsplash if the plan includes one. Chances are they'll each use a different tile product at a different size, so total them one at a time. The one place you do combine numbers is thinset and grout: add those up across the whole job and buy them as a single shopping list.
Not in a basic square footage estimate, no, but it does affect what actually happens on the floor. Wider grout lines mean fewer full tiles fit edge to edge before you hit a wall, so more of them get trimmed down at the perimeter. A 3/8 inch joint on a small room can nudge real waste a bit above whatever a plain area calculation told you to expect.
Start at 10%. That covers a straight grid layout in a simple room and won't leave you short. Once you decide on diagonal, herringbone, or you're working around a room packed with fixtures, raise that number, because the layout you pick and the obstacles in the room drive waste more than the tile size ever will.