Let's not go into the pros and cons of granite over other types of countertop materials. Let's just assume that you have already made the decision to "go granite."
Is This a Granite Tile Countertop?To save money, many homeowners install granite tiles on their countertops. Rather than using mortar and grout, these tiles are butted up edge-to-edge and affixed with epoxy. Essentially, these are floor tiles used for counter purposes. While inexpensive, this is an imperfect, not-so-high-end install because you typically want to limit the number of seams you have on kitchen counters. But again: cheap.
About $4.00 per square foot, for black granite 3/8" thick, materials only.
Is This Modular Granite?A big step up from the DIY granite tile method described above, modular granite is made especially for motivated DIY'ers. Modular granite "thinks ahead" to what you will need in installing granite: bullnoses, backsplashes, etc. Seams are narrower, less apparent. Slabs address things like corners.
About $25 per square foot and up.
Is This Slab Granite?Slab granite is the highest of the high end. As the name implies, this countertop material comes in giant slabs that are fabricated off-site (away from your home) and brought in. Slab granite installation is never a DIY job, so you must always figure in the high cost of professional installation. Transportation is costly, too, because of the dimensions of the material.
You will find companies claiming to install slab granite for $30 per square foot, but a more realistic figure doubles that to:
About $60 per square foot or more installed.