Fibonacci levels are commonly observed ratios between the size of a main trend and retracements. The main ratios are 38. 2%, 50%, 61. 8%, 100% and 161. 8%. These ratios are derived from the number series named after the Italian mathematician: 1,1,2,3,5,8,13, 21. . . If the first term is divided by the one to the right of it, the result gets nearer and nearer to 0. 618, a ratio that recurs in nature and art. Fibonacci levels are used in the weird and wonderful Elliott Wave Theory.