Select a point at which to commence measuring. For example, this may be the end of the countertop or a point part way along it where a cut-out is required to install a sink. When measuring countertops, linear feet traditionally are measured along the longest axis of the board rather than across the width.
Place one end of the tape measure against the starting point and hold it in place with one hand.
Lay the tape measure on the countertop surface and stretch it tight to form a straight line. Note the 1-foot or 12-inch line on the tape and make a mark on the countertop at this point. You have measured 1 linear foot of countertop.