Open Question: How do I work out how far i need to fall to break my neck?

Say i was hanging from a solid support. how long would the drop need to be to break my neck? assuming that the support and rope are strong enough and the knot is in the right place. I know it depends on my weight so is there an equation or anything i can use to work it out?? i found a table of weights and drops online but im not sure they are right so i just wanted to check. Only answer the