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Tile Grout Calculator

Find how much grout your tile job needs.

How it is calculated

Tile length, tile width, joint width and joint depth are all entered in inches, and the covered area in square feet. First the tool finds the grout per square foot: lb per sq ft = ((L + W) ÷ (L × W)) × joint × depth × 9.5, where L and W are the tile sides. The fraction (L + W) ÷ (L × W) is proportional to the total length of joint lines per unit of area, so smaller tiles give a larger value. The total is grout = lb per sq ft × area, shown in pounds to one decimal. All five inputs must be greater than zero. Fractions of an inch must be typed as decimals, for example 0.125 for 1/8 inch. The result is a net estimate with no allowance for waste, uneven tile edges or grout left in the bucket, and different grout types vary in density.

Worked example

You tile 100 sq ft with 12 × 12 inch tiles, a 0.125 inch joint (1/8) and a joint depth of 0.25 inch (1/4). Joint-length factor: (12 + 12) ÷ (12 × 12) = 24 ÷ 144 = 0.1667. Multiply by 0.125, then 0.25, then 9.5, which gives about 0.0495 lb per square foot. Multiply by 100 sq ft: 4.95 before rounding. The tool shows 4.9 lb of grout, and buying a little extra is sensible.

Try this example →

Common mistakes

  • Typing the joint as 1/8 or 3 mm. The field wants inches as a decimal, so 1/8 inch is 0.125 and 3 mm is about 0.118.
  • Entering tile size in centimeters or the area in square meters. Tiles are in inches and the area in square feet; 10 m² is about 108 sq ft.
  • Using the tile thickness as the joint depth without checking. The depth is how deep the grout actually fills, which can be less than the tile thickness.
  • Ignoring waste. The figure is a net amount; mixing losses and uneven tiles mean you need more.
  • Assuming that doubling the tile size halves the grout. Tile length and width both matter, and a rectangular tile is not the same as a square one of equal area.

About this calculator

This calculator uses the standard grout-coverage formula published by tile and grout manufacturers: pounds needed = [(tile length + tile width) ÷ (tile length × tile width)] × joint width × joint depth × 9.5 × area (sq ft), with tile and joint dimensions in inches. The 9.5 factor turns the joint volume per square foot (in cubic inches, over 144 square inches) into pounds of sanded grout. It is a net amount with no built-in waste allowance, so add your own. Smaller tiles need proportionally more grout than large ones for the same area, because more of the surface is taken up by joints.

Tile setters and DIY renovators use this before a job to buy the right number of bags and avoid a mid-project run to the store, or a large, wasteful leftover. It also lets you compare how much grout a wide grout line (common with rustic or handmade tile) will cost versus a tight, minimal joint.

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  • Editorial team

    Tile size drives the result far more than you might expect. Over 100 sq ft with a 0.125 inch joint and 0.25 inch depth, 12 inch tiles need about 4.9 lb while 2 inch mosaic tiles need about 29.7 lb. The answer is in pounds, so compare it with the net weight printed on the bag, round up to whole bags, and keep a little spare for later repairs. Which tile size and joint are you planning?

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