Formula to find lenght of material I need to make a sprint

Question

could somebody write me if you know how to calculate the lenght of a material i need to make a certain spring. I need any true formula you have.

Answer 1

$2\pi R\cdot n + n\cdot 26\text{mm} = \text{length of wire}$

$R=$ radius of loop

$n=$ no. of loops

the angle the loops make with the ground with the base is approx. = 0 so it can be neglected.now the radius of the wire is 13 mm so each loop will need 26mm of more wire. This extra length is needed to move to next loop. (precise calculation can be made by using volume but, i don't think that is the aim here)

Answer 2

One easy approximation is to assume that when your spring is fully compressed, it is essentially $n$ circles of radius $r$ where $n$ and $r$ are parameters for your spring (and $n$ can be fractional). Then the length you need is $2\pi rn$. This is very close to the "true" length assuming your material is very thin.