Although it's been close to eighteen years since I dissected my first cadaver in anatomy class, I still remember being surprised when I got my first glance at a pair of kidneys - they were much smaller than I had expected. Up until that point, I had imagined the kidneys to be quite large, given the amount of work that they are responsible for.
Each of your kidneys is about 4 to 5 inches long and about 1 inch thick, weighing in at about 4.5 to 5 ounces. To put it into easy-to-visualize terms, each of your kidneys is a bit larger than a deck of cards. Read more about How to Keep Your Kidneys Healthy as You Age