The stress is given by
where F {\displaystyle {\mathbf {F} }} is the force, A {\displaystyle {\mathbf {A} }} is the area, and σ i j {\displaystyle \sigma _{ij}} is the stress tensor, given by
where where σ x {\displaystyle \ \sigma _{x}} , σ y {\displaystyle \ \sigma _{y}} , and σ z {\displaystyle \ \sigma _{z}} are normal stresses, and τ x y {\displaystyle \ \tau _{xy}} , τ x z {\displaystyle \ \tau _{xz}} , τ y x {\displaystyle \ \tau _{yx}} , τ y z {\displaystyle \ \tau _{yz}} , τ z x {\displaystyle \ \tau _{zx}} , and τ z y {\displaystyle \ \tau _{zy}} are shear stresess.
is the force,
is the area, and 
is the stress tensor, given by
![{\displaystyle \sigma _{ij}\equiv \left[{\begin{matrix}\sigma _{x}&\tau _{xy}&\tau _{xz}\\\tau _{yx}&\sigma _{y}&\tau _{yz}\\\tau _{zx}&\tau _{zy}&\sigma _{z}\\\end{matrix}}\right]}](https://wikimedia.org/api/rest_v1/media/math/render/svg/5b170735cb100939c7da5c30aa215add87dcf051)
, 
, and 
are normal stresses, and 
, 
, 
, 
, 
, and 
are shear stresess.