Measure the length of a shelf in your kitchen that is, or could be, used for storage. Hook the bent end of a builder's tape measure over one end of the shelf and measure the distance to the opposite end. If your tape doesn't have a bent end, either hold it with one hand or pin it down with a convenient weight such as a can of food. Stretch the tape tight so it is a straight line with no bends or sagging. Read and record the length of the shelf.
Repeat Step 1 with every other shelf in the kitchen, including those inside cupboards and larders. Record each length as you measure it.
Add the individual lengths together to determine the overall linear feet of kitchen storage. For example, a kitchen containing two 10-feet-long shelves and three cupboards, each containing two 3-foot shelves has a total of 38 linear feet of storage -- (10 x 2) + 3 x(2 x 3) = 38.