Step by step
Multiply length by width for the floor area in square feet. Add a waste allowance, commonly around 10% for straight layouts and more for diagonal or patterned ones. Divide by the area of one piece and round up. If pieces come in boxes, round the box count up too.
Worked example
A room 12 by 9 feet is 108 square feet. Add 10% for waste to get 118.8. If each tile covers 0.75 square feet, you need 159 tiles. At 12 tiles per box that is 14 boxes (168 tiles), leaving 9 spare.
Spare tiles are useful. Keep them from the same production lot so a repair years later matches in color.
Irregular rooms
Split an L-shaped or odd room into rectangles, measure each one and add the areas. Include closets, alcoves and the space under doorways if the flooring continues into them.
Mistakes to avoid
Measuring once. Skipping the waste allowance. Buying the exact amount and then finding the store has no more of that lot. Forgetting that the installer's required allowance may differ from yours; ask them before you order.
Try the calculator
Run your own numbers in the free flooring and tile calculator. It works in your browser and nothing you enter is saved or sent.
Common questions
How do I get the area of one tile?
Multiply its length by its width in feet. A 12 by 12 inch tile is 1 square foot.
Does this include underlayment?
No. Underlayment and trim are separate materials.
What waste percentage is typical?
It depends on layout and material. Check the manufacturer's instructions or ask the installer.
This guide is general information, not financial, tax or legal advice. Rates, fees and rules change, so confirm current terms with the lender, store or agency involved. All dollar figures are invented examples.