Hi, what is the minimum length that a string needs to be when it is originally tied? I’ve seen different measurements, some from the first knot and some from the last. I’m not sure what the halacha is. Thanks.

ב"ה Shalom The length of Tzizit from the wound part of the tzizit (the "gdil") until the end of the strings must be at least 12 thumb breadths= agudalim according to the Shulchan Aruch (Orach Chaim 11:4) There are different opinions how much is a thumb breadth. Many hold that they must be 24 centimeters (which is approximately 9.45 inches) long from the wound part of the tzizit until the end of the strings. Others hold they must be 12 inches long which are approximately 30 centimeters.(See Tzizith- A thread of Light , by Rabbi Aryeh Kaplan zt"l' pgs. 20-24) All the best