Two nickels, which are worth 5 U.S. cents each, equal one dime, which is worth 10 U.S. cents. The diameter of a nickel is 0.835 inches with a width of 1.96 millimeters, while a dime is smaller, at 0.705 inches in diameter and 1.35 millimeters in thickness.
A nickel contains more of its namesake metal, with a content of 25 percent nickel and 75 percent copper. A dime contains only 8.33 percent nickel in its construction, with copper comprising the rest. The dime was introduced in 1946, and the current incarnation of the nickel, known as a "Jefferson nickel" because of the former president's portrait on the obverse, entered circulation in 1938.