Tongue and groove flooring employs a simple system to "lock" individual sheets or planks together. A tongue on one side of a piece of flooring locks into a matching groove on the side of the adjacent piece. The joint, which is hidden when the pieces are pushed together, strengthens the bond and prevents drafts moving between the planks or sheets. Measuring for tongue and groove flooring is straightforward and does not require previous building experience.
Divide the floor area into rectangles. It is easier to calculate the areas of rectangles than it is to calculate the areas of irregular shapes. If the room is rectangular treat it as a single rectangle, but if it is "L" shape, break it into two rectangles. Nooks, window bays and similar irregularities can also be treated as separate rectangles.
Measure the width and length of each rectangle. Convert measurements in feet and inches into decimal feet by multiplying the inches by 0.0833. This converts inches into a decimal value. For example, 12 feet and 7 inches is equivalent to 12.5831 feet because 7 x 0.0833 equals 0.5831.
Multiple the width by the length for each rectangle to determine the surface area. If there is more than one rectangle, add together the areas of all the rectangles to determine the total surface area. For example, a room consisting of three rectangles with areas of 144, 12 and 72 square feet has a total floor area of 228 square feet.
Determine the area of an individual piece of tongue and groove flooring. For example a plank measuring 6 feet long and 6 inches wide has a surface area of 3 square feet (6 feet x 0.5 feet).
Divide the total surface area by the area of a single piece of flooring. Round up to the next whole number. The result is the number of pieces of tongue and groove flooring required to complete the project. For example, a room with a floor area of 228 square feet requires 76 tongue and groove planks measuring 6 feet long by 6 inches wide.