How to calculate tile
To count tiles, work out the area, add waste for the layout, and divide by the space one tile takes up, including its share of the grout joint. Boxes come from the coverage on the label. Thinset comes from the trowel notch, since bigger notches put down more mortar per square foot.
Tiles = area x (1 + waste %) / tile + joint, rounded up
Thinset bags = area / coverage per bag for the trowel
Worked example: 180 sq ft of 12 x 24 tile
With 10% waste you need 198 sq ft. Each 12 x 24 tile with a 1/8" joint takes up 12.125 x 24.125 / 144 = 2.03 sq ft, so 198 / 2.03 = 97.5, or 98 tiles. At 16 sq ft per box that is 13 boxes, and with a 1/2" notch at about 40 sq ft per 50 lb bag, 5 bags of thinset.
Assumptions
- Waste: about 10% straight or offset, 15% diagonal, 20% herringbone. Add more for small rooms and lots of cuts.
- Thinset coverage varies by product, substrate and back-buttering. The trowel figures are typical for a 50 lb bag; use the number on your bag.
- Grout, backer board, membrane and trim pieces are separate items.
Building these for a living? See Bolster for flooring and tile contractors, or how digital takeoff and AutoCost turn measurements into priced estimates.
FAQ
How do I calculate how many tiles I need?
Find the area in square feet and add waste, then divide by the area of one tile plus its grout joint. 198 sq ft of 12 x 24 tile with a 1/8" joint is 98 tiles.
How much extra tile should I order?
Around 10% for a straight or offset layout, 15% for diagonal and 20% for herringbone. Order from the same lot and keep a few spare tiles for repairs.
How much thinset do I need?
It depends on the trowel. A 50 lb bag typically covers about 90 sq ft with a 1/4 x 1/4" notch, 60 sq ft with 1/4 x 3/8" and 40 sq ft with 1/2 x 1/2". Large format tile that needs back-buttering uses more.
Does grout joint size change the tile count?
Slightly. A wider joint means each tile covers a little more floor, so you need fewer tiles. The effect is small for large tile and bigger for mosaics.
Can I turn this into a tile estimate?
Yes. Add unit prices here for a material total. In Bolster, AutoCost prices tile, setting materials and labor with live regional costs and builds the estimate and proposal.
