Draw a layout of your kitchen, including countertop, backsplash, sink and island positions and appliance locations. Use this to record measurements.
Use the tape measure to measure each section of countertop in inches. Measure length from end of counter to wall or point where next section of countertop begins. Measure depth, from wall or back of counter to front for each section as well. For galley kitchens, you'll measure from one end of counter to the other. For "L" or "U" shaped layouts, you will break it into rectangular sections at each corner.
Calculate odd-shaped sections or corner pieces by measuring from the longest point lengthwise and longest point depthwise. It may help to envision this odd-shaped portion as a square or rectangle. If you are retaining this feature in the countertop, the actual shape will be recreated during the installation process.
Measure the length and height of backsplashes. This will help to assure that you will estimate materials needed (tile, wallpaper, paint) for walls behind counters correctly.
Figure the area of each section by multiplying length by depth. Add the area of all sections together to determine total square inches. Divide total square inches by 144 to determine square footage. Multiply square footage by the retail square foot price of the countertop to determine your estimated cost of material needed.