The “Master Price and Time Calculator”, which is popularly known as the Square of Nine happens to be one of the most interesting discoveries by W. D. Gann. Square of Nine is pyramidal arrangement of numbers and possess great ability to forecast price and time cycles. This article is an attempt to summarise mathematical principles behind the Square of Nine. Below is a snapshot of the Square of Nine: 133 134 135 136 137 138 139 140 141 142 143 144 145 132 91 92 93 94 95 96 97 98 99 100 101 146 131 90 57 58 59 60 61 62 63 64 65 102 147 130 89 56 31 32 33 34 35 36 37 66 103 148 129 88 55 30 13 14 15 16 17 38 67 104 149 128 87 54 29 12 3 4 5 18 39 68 105 150 127 86 53 28 11 2 1 6 19 40 69 106 151 126 85 52 27 10 9 8 7 20 41 70 107 152 125 84 51...