How much tile do I need?

The arithmetic, and the one variable that is not the tile

Tile takes two counts, not one, and they run on different divisors. Boxes come from area times your waste factor divided by the square feet in a box. Mortar comes from the same area divided by the coverage figure for the trowel in your hand. The tile decides the first number. The trowel decides the second, and the trowel is the part nobody mentions until you are already at the register.

Work the eight by five floor this page opens with. Forty square feet, times 1.10, is 44. At 15 square feet to a box that is 2.93, so 3 boxes and 45 square feet delivered. For mortar, CUSTOM Building Products prints 85 to 95 square feet per 50 pound bag of VersaBond with a 1/4 by 1/4 by 1/4 square notch, and 60 to 67 with a 1/4 by 3/8 by 1/4. Forty square feet fits inside one bag either way.

That is worth pausing on, because it is the exception rather than the rule. On a small bathroom floor the notch costs you nothing. Cross 85 square feet and it starts costing you a bag at a time. On a 200 square foot floor the small notch is 3 bags and the larger notch is 4, same tile, same room, same installer, one different tool.

How much waste is technical, and how much is attic stock somebody sold you

There is no manufacturer figure for tile waste, and this site will not invent one. The ten percent this page starts you at is a common straight lay starting point and it is marked as yours, not as a claim.

What is technical is easy to reason about even without a published number. Cuts happen at the perimeter, so waste scales with how much perimeter you have per square foot, and with how big the tile is. A twelve by twenty four plank in a five foot wide room has a large fraction of its pieces cut. The same room in a small mosaic barely wastes anything, because the sheet cuts between the tiles. Diagonal and herringbone create two cuts where a straight lay creates one. That is the real mechanism, and it is why a single percentage is a starting point rather than an answer.

Attic stock is the other half. Keeping a few spare tiles from your own dye lot is genuinely smart, because a discontinued line cannot be matched at any price. But it is a decision, with a number attached, that somebody should say out loud. Folded silently into a box count it looks exactly like a padded order.

The point where a tile quote stops adding up

Two divisions, both done at the counter. Boxes times square feet per box divided by your area gives the waste factor actually used. Five boxes of 15 for a 40 square foot floor is 75 over 40, which is 1.87, and on a straight lay with no pattern that is a question, not an estimate.

Then the mortar. Your area divided by the bags quoted gives the coverage they assumed. If it lands below 60 square feet to a 50 pound bag, they are either planning to back trowel, which the technical data sheet says to estimate separately, or planning to use a bigger notch than you agreed to. Both are fine answers. Neither is fine unsaid.

Two bag sizes, two tag formats, and the number that makes them comparable

VersaBond is packaged in 50 pound and 25 pound bags, gray or white, and the coverage chart on the sheet is written per 50 pound bag only. So a 25 pound bag is not a small convenience, it is half the powder and therefore half the coverage, and comparing the two on shelf price alone is comparing nothing.

Put both on the same footing before you decide: price divided by the square feet that bag will actually cover at your notch. For the small square notch that is 85 to 95 for the 50 pound bag and roughly 42 to 47 for the 25. For the larger notch it is 60 to 67, and roughly 30 to 33. Now the two prices mean something.

The tile itself has the same problem in a different costume. The shelf tag is per square foot, the register is per box, and trim pieces, bullnose and pencil liners are per piece. Convert the tag to a box price by multiplying by the square feet printed on the carton, then divide your rounded box count by your actual floor area for your real cost per square foot. On the floor above, 3 boxes cover 45 square feet of a 40 square foot room, so your true cost per square foot sits about twelve percent above the tag before anyone has done anything wrong.

Coverage under the tile, which is the part you can actually inspect

This is the single most useful line on the technical data sheet, and it is a quality rule that happens to be a quantity rule. Mortar coverage between the substrate and the underside of the tile is required to be 80 percent or better in dry areas, and 95 percent or better in wet areas and exteriors, with every tile edge properly supported, in a bed of at least 3/32 of an inch and no more than 1/4 inch for mortars without an ANSI H rating.

The sheet then tells you how to check it, and you can do this yourself while the job is happening: periodically pull up a tile you have just set and look at the back. If it has skinned over and is no longer sticky, recomb it with the notch trowel. If it has gone dry, scrape it off and use fresh material.

The same paragraph is where the extra mortar comes from. Larger tiles, tiles with a deep pattern moulded into the back, and ungauged natural stone may need a larger notch and may need to be flat back troweled to reach that coverage, and CUSTOM says plainly that when you back trowel you should estimate the extra thickness and add it to your order. So if your tile is big, more mortar is not somebody upselling you. It is the manufacturer's instruction, and the sheet is free to read.

What sits on the receipt beside the tile and the mortar

• Grout, whose coverage depends on your joint width, your tile size and your tile thickness, which is why no single figure covers it and why this page does not print one.
• Backer board and its fasteners where the substrate calls for it, plus mesh tape for the board joints.
• Waterproofing in wet areas, and a primer coat where the sheet requires one. Over lightweight cement or gypsum surfaces VersaBond's own instructions call for a sealer or a primer coat of RedGard diluted one part to four parts water before anything else happens.
• Movement joints. The sheet says construction, expansion and isolation joints must never be bridged with setting material. They come through the tile work and get filled with an elastomeric sealant, per TCNA EJ171. That is a separate product and a separate line.
• The tools. The notched trowel in the size you actually chose, spacers, a beating block and rubber mallet, which the sheet names in the setting instructions, and a blade for the wet saw that will be duller at the end of the day than it was at the start.

The price range above, and why tile is the shakiest one on this site

Coverage, pot life, water and required bond percentages are published, dated and free to open. The dollar range is read a different way, off product pages at Sutherlands, a home improvement and lumber chain out of Kansas City, Missouri whose pages publish a price for every one of its stores instead of one national number. These are the pages, read on 2026-08-23:

• Shaw Omega ceramic tile, 13 by 13 inch grey, 16.47 sq ft per carton, item 1451541: 16.30 dollars at the 1 store with it in stock. Open the product page.
• Shaw Omega ceramic tile, 17 by 17 inch bone, 8 pieces per box, item 2795110: 22.37 dollars across the 3 stores with it in stock. Open the product page.
• Daltile Elect glazed ceramic tile, 12 by 24 inch white, 8 pieces per carton, item 3063906: 27.69 dollars at the 1 store with it in stock. Open the product page.
• CUSTOM Building Products VersaBond fortified thin-set mortar, grey, 50 lb, item 3811130: 14.96 to 19.99 dollars across the 8 stores with it in stock. Open the product page.

Now the honest warning, and on this page it matters more than on any other. Tile swings harder than almost any material in the house, because the same square foot of porcelain is sold as a builder line and as a designer line, and the four readings above are all at the plain end of that shelf. A box you fall in love with can be three times the top of that range and nothing has gone wrong. The thin-set reading is far steadier, because a 50 pound bag of mortar is a commodity and a tile is a decision. Either way the tag in front of you outranks the page: type it into the price field and every figure reruns on your number.

Sources for every figure above: CUSTOM Building Products, VersaBond Professional Thin-Set Mortar, technical data sheet TDS-119, published 12/12/2023, custombuildingproducts.com/TDS/TDS-119.pdf, opened 2026-08-23, for coverage, pot life, water and bond. Sutherlands, the four product pages linked above, read 2026-08-23, for every dollar figure.