Tile Calculator
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Find out how many tiles, thin-set mortar bags, and pounds of grout you need from room dimensions or square footage — by tile size, layout, and joint width.
Quick answer: A 100 sq ft room tiled with 12×12 in. tiles in a straight/grid layout needs about 110 tiles after the standard 10% wastage allowance, roughly 2 bags of thin-set mortar (at approximately 80 sq ft per 50 lb bag), and about 15 lbs of grout with a standard 1/8 in. joint.
Total Tiles Needed
Includes layout wastage allowance
Suggested grout purchase:
📐 Formula
Tiles per sq ft = 1 ÷ (tile width in ft × tile height in ft). Total tiles = ceil(area ÷ sq ft per tile × (1 + wastage %)). Thin-set mortar bags = ceil(area ÷ 80 sq ft per 50 lb bag). Grout (lbs) ≈ area × grout factor, which increases with joint width and decreases with tile size.
How to Use the Tile Calculator
Choose area or room-dimensions mode
Enter a direct square footage if you already know your tiling area, or switch to room-dimensions mode and enter length and width so the calculator can multiply them into area for you.
Select your tile size
Choose from common US sizes — 12×12 in., 18×18 in., 24×24 in., or 6×24 in. plank-style — since tile size directly determines how many tiles are needed per square foot.
Choose your layout pattern
Pick straight/grid layout (10% wastage) or diagonal/herringbone layout (15% wastage), since diagonal cuts at wall edges waste more material per tile.
Select grout joint width and review results
Choose your grout joint width, then review the total tile count, thin-set mortar bags, and estimated grout needed for your order.
Why Tile Size Determines How Many Tiles You Need
Every tile size covers a different amount of floor or wall area, so the number of tiles per square foot swings widely across common formats. A 12×12 in. tile covers exactly 1 sq ft, so a 100 sq ft room needs roughly 100 tiles before wastage. Step up to an 18×18 in. tile and each piece covers 2.25 sq ft, cutting the base tile count to about 44 for the same room. Go bigger still, to a 24×24 in. tile, and each piece covers a full 4 sq ft — the same room needs only about 25 tiles. A 6×24 in. plank-style tile covers 1 sq ft per piece, the same as a 12×12 in. tile, but its narrow shape produces more linear feet of grout joint per square foot, which is why plank tile also carries a slightly higher grout estimate than a square tile of the same area.
If you're not certain of your room's exact dimensions before you start pricing tile, our square footage calculator can help you get an accurate area first.
Why Wastage Percentage Matters
The wastage percentage isn't just a cushion for cutting mistakes — it also protects against a problem that has nothing to do with your own workmanship: batch and shade variation. Tile is manufactured in production runs called batches, and even tiles from the same product line can differ slightly in shade, tone, or exact dimension between batches. If you order exactly the number of tiles the room requires and later need a few more — because of a miscut, a broken tile, or a mismeasurement — the replacement tiles may come from a different batch and visibly clash with the original installation. Buying your full order, including the wastage allowance, from a single batch is the only reliable way to guarantee consistent color and size across the whole job. That's also why the wastage buffer covers more than physical cutting waste: it includes an allowance for breakage during handling and installation, plus a few spare tiles held back for future repairs, so a cracked tile years later can be matched exactly instead of forcing a whole-room re-tile.
Why Diagonal and Herringbone Layouts Need More Tiles
A straight or grid layout runs tile edges parallel to the walls, so the only cuts needed are at the room's actual boundary — a clean, mostly-straight cut that wastes only a thin sliver of each edge tile. A diagonal layout, by contrast, sets every tile at a 45° angle to the walls. That means almost every tile touching a wall or corner needs an angled cut instead of a straight one, and each of those angled cuts typically discards close to half a tile rather than a narrow strip. Herringbone patterns, which interlock rectangular tiles at alternating 90° angles, create a similar effect at the room's perimeter for the same underlying reason — the pattern itself doesn't align cleanly with a rectangular room's edges. Multiply that extra loss across every wall and corner in the room and the difference adds up fast, which is why this calculator applies a 15% wastage allowance to diagonal and herringbone layouts instead of the 10% used for a straight grid.
Worked Example: Tiling a 100 Sq Ft Bathroom Floor
Take a 100 sq ft bathroom floor being tiled with 12×12 in. tiles in a straight/grid layout, using a standard 1/8 in. grout joint:
Tiles per sq ft = 1 ÷ (1 ft × 1 ft) = 1 tile per sq ft.
Tiles before wastage = 100 sq ft × 1 tile/sq ft = 100 tiles.
Total tiles with 10% wastage = ceil(100 × 1.10) = 110 tiles — matching the Quick Answer above.
Thin-set mortar = ceil(100 ÷ 80 sq ft per bag) = 2 bags (50 lb bags).
Grout ≈ 100 sq ft × 0.15 lbs/sq ft (12×12 in. tile, 1/8 in. joint) = 15 lbs, which rounds up to a single 25 lb bag.
A larger or smaller room scales the same way — double the area and you'll need roughly double the tiles, mortar, and grout, since all three quantities are driven directly by square footage.
Choosing the Right Tile Size for Your Room
Tile size isn't purely a style choice — it also affects how much cutting a room requires and how forgiving the substrate needs to be. Smaller tiles, such as 12×12 in., handle tight or irregular spaces well because they need fewer full-tile cuts around fixtures like toilets, vanities, and tub surrounds, which makes them a common choice for small bathrooms. Larger-format tiles, such as 24×24 in., use fewer grout lines and can make an open room feel more expansive, but they demand a much flatter substrate — even minor floor unevenness becomes visible under a large, rigid tile — and cost more to cut precisely around obstacles. The 6×24 in. plank-style format sits in between on cost and cutting complexity, and is popular for wood-look flooring in hallways and living areas where a long, linear pattern reads naturally.
| Tile Size | Sq Ft per Tile | Tiles per Sq Ft | Best Use |
|---|---|---|---|
| 12×12 in. | 1.00 | 1.00 | General floors, small bathrooms, most rooms |
| 18×18 in. | 2.25 | 0.44 | Living areas, larger rooms |
| 24×24 in. | 4.00 | 0.25 | Large open areas, modern minimal look |
| 6×24 in. (plank) | 1.00 | 1.00 | Wood-look flooring, hallways |
Thin-Set Mortar and Grout: What the Numbers Mean
Thin-set mortar is the cement-based adhesive that bonds tile to the substrate, sold in the US in standard 50 lb bags. The approximately 80 sq ft per bag figure used here assumes a 1/4 in. notched trowel on standard-size floor and wall tile — a reasonable, commonly-cited coverage rate, but not a precise universal constant. Larger-format tile, a thicker trowel notch for extra-flat leveling, or a more absorbent substrate can all push real-world coverage below 80 sq ft per bag, so it's worth budgeting an extra bag on a large job rather than cutting the order exactly to the calculated minimum.
Grout is trickier to estimate precisely, since consumption depends on both tile size and joint width — smaller tiles and wider joints both mean more linear feet of joint per square foot, and therefore more grout. The lbs-per-sq-ft factors used in this calculator are estimates based on typical published figures, not a single fixed rate. Once you know roughly how much grout you need, check your specific grout product's coverage chart for a more precise order, since sanded and unsanded formulas, and different manufacturers' mixes, can vary meaningfully from a generic estimate. If you're planning a full room renovation rather than just the floor, it's worth working out wall paint needs too — our paint coverage calculator covers gallons needed by room dimensions, and you can browse every tool in this category on our renovation calculators hub.
Frequently Asked Questions
Tiles per square foot depends entirely on tile size, calculated as 1 ÷ (tile width in feet × tile height in feet). A 12×12 in. tile covers exactly 1 sq ft, so you need 1 tile per sq ft. An 18×18 in. tile covers 2.25 sq ft, needing about 0.44 tiles per sq ft. A 24×24 in. tile covers 4 sq ft, needing 0.25 tiles per sq ft. Always add a wastage percentage on top of this base count before ordering.
Standard thin-set mortar is sold in 50 lb bags and typically covers around 80 sq ft when applied with a 1/4 in. notched trowel for standard-size floor and wall tile — divide your total area by 80 and round up to the next whole bag. This figure is approximate and varies by mortar brand, trowel notch size, and substrate texture, so check your chosen product's coverage chart before finalizing an order, especially for large-format tile.
Use 10% wastage for a straight or grid layout in a rectangular room with few obstacles — it covers ordinary cutting waste plus a small buffer for breakage and future repairs. Use 15% for diagonal or herringbone layouts, since the 45° cuts at every wall edge lose more material per tile. Rooms with many corners, alcoves, or fixtures like tubs and vanities should also lean toward the higher 15% figure regardless of layout.
A diagonal or herringbone layout runs tiles at a 45° angle to the walls, which means almost every tile touching a wall or corner needs an angled cut rather than a clean straight cut. Each of those cuts typically wastes close to half a tile instead of a thin sliver, so the extra material adds up fast across a room's full perimeter — which is why diagonal and herringbone patterns use a 15% wastage allowance instead of the standard 10%.
Smaller tiles, such as 12×12 in., generally work best in small bathrooms because they need fewer cuts around fixtures like toilets, vanities, and tub surrounds, and they handle tight, irregular spaces more gracefully. Larger format tiles, such as 24×24 in., can visually enlarge a small room with fewer grout lines, but they require a very flat substrate and more precise cutting around obstacles, which can increase both material waste and labor cost in a cramped layout.
Sources & Methodology
Coverage rates used in this calculator are based on typical published figures from major US thin-set mortar and grout manufacturers, not a government or standards body — home-improvement figures like these come from the manufacturers themselves rather than a regulator, the same as the other calculators in this category. The approximately 80 sq ft per 50 lb bag thin-set figure and the grout lbs-per-sq-ft estimates reflect commonly cited coverage rates from brands including Custom Building Products and Mapei. Always check the specific product's label or spec sheet, since exact coverage varies by product line, trowel notch size, and joint width.