The most popular standard tiles are 12" by 12", although tiles are made in 12" by 24" and some other sizes. Most are made with tongue and groove edges for easier applications. Plain, embossed and patterned finishes are available, and some are molded with special texturing and square edges (instead of the common beveled edges) to make seams almost disappear when in place.
Acoustical tile is made from the same type of fiber, but undergoes an additional manufacturing process which helps it absorb much of the sound in a room. A well-designed acoustical tile can absorb up to 70% of the excess noise in an area.
Your retailer can help you estimate the materials you need for a tile installation, and most manufacturers provide charts to the retailer to help estimate the number of tiles, the amount of furring and the gallons of adhesive needed, depending on room size.
Manufacturers will normally pack 12" by 12" ceiling tiles 40 to a carton, with 12" by 24" tiles packed 20 to a carton.