These charts show the number of pounds of grout per square foot of the tile needed when a certain size tile and a certain joint width are used. In order to find out how many pound of grout you will need, multiply the number from the table times the number of square feet of tile you will be installing.
For example, a 3/8″ x 3/8″ x 3/8″ tile and a 1/16″ joint width will require 0.94 pounds of grout per square foot. If you are covering an 8′ x 12′ floor, you will need 96 square feet of tile. 0.94 time 96 yields 90 pounds of grout required for the complete job. Based on the packaging available, the correct amount of grout to order would be 100 pounds (four, 25 pound bags).
These charts are based on filling the joint to their full depth, the nominal tile dimensions, and a 10% waste factor. Actual coverage may vary.