# Spring Diameter

Written by Jerry Ratzlaff on . Posted in Fastener

## formulas that use Spring Diameter

 $$\large{ D = D_o - d }$$ $$\large{ D = D_i + d }$$ $$\large{ D_i = D_o - 2 \; d }$$ $$\large{ D_o = D_i + 2 \; d }$$ $$\large{ D_o = \sqrt{ D^2 + \frac{ p^2 \;-\; d^2 }{ \pi^2 } } + d }$$ (When a spring is compressed there is a small increase in $$D_o$$.  When a spring tolerance is required, this formula will give you the increase in $$D_o$$.)

### Where:

$$\large{ D }$$ = mean coil diameter

$$\large{ D_i }$$ = inside diameter

$$\large{ D_o }$$ = outside diameter

$$\large{ \pi }$$ = Pi

$$\large{ p }$$ = pitch

$$\large{ d }$$ = wire diameter

Tags: Equations for Spring