For large-format floor tiles, use a 1/2 inch square-notch trowel and plan for 12% waste.
How to calculate tiles
Start by measuring each surface you want to tile. Measure floors wall to wall and walls from the floor or countertop to where the tile will stop. Break awkward shapes into rectangles and add them up, then subtract large areas you will not tile, such as a bathtub, a shower door opening or a kitchen island. TileMath divides the total by the area of one tile plus its share of the grout joint, adds a waste allowance for cuts and breakage, and rounds up to whole tiles and whole boxes.
How much waste to allow
Every layout needs some cut tiles at the edges. A straight grid with tiles aligned to the walls wastes the least, usually around 10%. Brick or offset patterns need a little more because every other row starts with a cut. Diagonal layouts waste around 15% because every edge tile is cut on an angle, and herringbone or chevron patterns can need 20% or more. Add a few percent more for natural stone, handmade tiles and first-time DIY projects, and keep a few spare tiles from the same production lot for future repairs.
Grout and thinset
Grout quantity depends on the length of joints per square metre, which rises sharply as tiles get smaller, and on the joint width and depth. A 12 × 12 inch tile with a 1/8 inch joint needs very little, while 1 inch mosaics with the same joint need several times more. Thinset mortar is estimated from the trowel size: small wall tiles use a 3/16 inch V-notch, standard floor tiles a 1/4 × 3/8 inch square notch, and large-format tiles a 1/2 inch notch, sometimes with back-buttering. Coverage figures are typical values for a 50 lb bag; always check the manufacturer’s chart.
Before you buy
Check that your floor is flat and stiff enough for the tile you choose, plan where cut tiles will fall so they are not tiny slivers at a doorway, and dry-lay a row to check your joint spacing. Order all the tile at once so it comes from the same batch. Your measurements are stored only in this browser.
Frequently asked questions
Should I tile under the fridge?
Usually yes, so the appliance can be moved and the floor stays level.
How do I measure an L-shaped room?
Split it into two rectangles and add both.
What size tile for a small bathroom?
Larger tiles with thin joints often make small rooms look bigger.
Is TileMath free?
Yes, with no sign-up or ads.
Are my measurements saved?
Yes, in this browser only.