How this calculator works
Each tile occupies its own area plus one grout joint, so tiles = area × (1 + waste) ÷ (tile + joint). Grout fills the joints. We calculate the volume of joint per square foot from the tile size, joint width and tile thickness, and convert to weight with a grout density of about 100 lb per cubic foot, plus 20% for waste. Thinset coverage depends on the notch size of the trowel.
Worked example: a 12 × 10 ft floor (120 ft²) in 12 × 12 in tiles, 1/8 in joints, 10% waste: you need 130 tiles (13 boxes of 10), about 9.4 lb of grout (one 25 lb bag) and 2 bags of thinset with a 1/4 × 3/8 in trowel.
Tips before you buy
- Buy all tiles from the same production lot (check the lot or shade number on each box). Colour and size vary between lots.
- Large-format tiles (over 15 in) and natural stone need more waste, a flatter substrate, and usually a larger trowel and back-buttering.
- Sanded grout is for joints 1/8 in and wider, and unsanded for narrower joints and delicate surfaces.
- Unlike flooring, tile is hard to match later. Buy a spare box.
Quick answers by size
Tools & materials for this project
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Frequently asked questions
How many tiles do I need for 100 square feet?
Divide 100 by the area of one tile (plus its joint) and add 10%. For 12 × 12 in tiles with 1/8 in joints that is about 108 tiles.
How much grout do I need?
It depends on tile size, joint width and thickness. Small tiles and wide joints need much more. A 25 lb bag covers a few hundred square feet of 12 in tile with narrow joints, but only a fraction of that for mosaics.
How much thinset do I need per square foot?
A 50 lb bag covers roughly 45 to 95 ft², depending on the trowel notch. Large tiles on a large notch use the most.
How much extra tile should I buy?
10% for straight layouts, 15% for diagonal layouts, and more for intricate patterns or natural stone.
Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.