How long is a foot?

My favorite kind of question. This is actually a "dumb" question with a really complicated answer. The length of a foot had no universal meaning until relatively recently. A foot was 12 inches long, and an inch was defined as either the width of a man's thumb or three barleycorns laid end-to-end. Neither of which is helpful. Your thumb or my thumb? 2 row barley or 6 row barley? Construction sites had a board set up with the length of the inch, rod, foot, and yard that was the official lengths for that site. There was some codifications of a "universal" foot that everyone had to use, but there were regional variations and no one could pick one exact measurement. The Normans used the Carolingian measurement of the ancient Roman length of 11.65 modern inches or 296mm. The French used this measurement up until they switched to metric. The Anglo-Saxons used a German measurement of 13.2 modern inches or 335mm. Edward the II picked the size of the foot equal to our modern standard, allegedly. Allegedly. The Italians had a different scale on how big an inch was depending on what city you were in. The Spanish used the Arabic system until Ferdinand and Isabella, then they switched over the system used in the Vatican and kept it until Franco took over.