Potassium hydrogen phthalate, also known as KHP, is a volumetric standard manufactured under stringent conditions and measured with the highest possible precision. Its mass fraction is determined by potentiometric titration, and it is qualified in a DIN EN ISO/IEC 17025 accredited laboratory.

It finds its use as a certified reference material (CRM) for the standardization of volumetric solutions in alkalimetric titrations, according to Ph. Eur. It is also used to prepare a standard solution in determination of COD.