How to Estimate Grout Needs. Grout, often called mortar, is key to successful tile installation. Determining how much you need to complete a tile project is the first step towards its completion. You can take the guesswork out of this process by using a grout calculator and getting your measurements right.
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Determine the square footage of the area being tiled. Multiply the length times the width of your area. The resulting number is the square footage that you need to grout.
Establish the size of the tiles you are using in your installation. The smaller the floor tile, the more grout you need.
Measure the height of the tiles. Before you can accurately determine how much grout will be used, you need to know how deeply the grout will be applied.
Use an online grout calculator to get a reliable estimate of how much you'll need. Enter the information from Steps 1, 2 and 3 and record the number.
Purchase slightly more grout or mortar than needed just to insure you have what you need. It is better to have more than you need to complete your mortar instillation than to not have quite enough.