Converting electric field to electric potential (voltage)?

Hello, I have a problem where I am working with piezoelectric materials. I have done all the work and solved the problem and such, but I don't know how to convert the resulting electric field in the material due to a certain deformation into a potential. I realize this is probably a pretty elementary conversion that involves the thickness of the material or perhaps the cross-sectional area, but I don't know offhand how to convert this to a useful voltage value. Thanks for any enlightenment.