The deformation $\mathrm{\delta }$ of an axial member is given by:

$\mathrm{\delta }=\frac{\mathrm{FL}}{\mathrm{AE}}$

where $\mathrm{F}=$ internal force, $\mathrm{L}=$ member length, $\mathrm{A}=$ cross-sectional area, and $\mathrm{E}=$ elastic modulus.

This formula applies only to axial members where $\mathrm{F}$, $\mathrm{A}$, and $\mathrm{E}$ are constant.