The ’amah is the distance from the tip of the elbow to the tip of the middle finger, that is, about 50 centimeters or 18 inches. There is also a longer cubit mentioned in Ezekiel (see tefach above, Palm).
EZK 41:8: The Hebrew text here speaks of an ’amah ’atsilah. The word ’atsilah is problematic, perhaps referring to a length, or perhaps having something to do with a foundation or a terrace. Translations generally treat it as a length, something that qualifies the length of a cubit: “a long cubit” (so RSV). Others indicate this by giving a longer length for the rod than someone might expect, for example, “ten and one-half feet” (NCV). If it is felt to be significant that a non-standard cubit is being used here, then this latter solution will be unacceptable.