The UCUM (Unified Code for Units of Measure) is a system for coding units of measure. The purpose of UCUM is to facilitate unambiguous electronic communication of quantities together with their units. The focus is on electronic communication, as opposed to communication between humans.

UCUM is both a code system of atomic units of measure (e.g. g, mg, etc.) and a syntax standard for how to represent precoordinated units of measure (e.g. g/ml, mg/dl) from their atomic counterparts. UCUM also provides the computational foundation to convert between like units of measure by providing multipliers (e.g. convert from mg/dl to g/ml).

UCUM is commonly displayed to clinicians as part of quantitative laboratory results and as part of medication dose form. UCUM has been adopted internationally by many organizations such as IEEE, DICOM, LOINC, and HL7, and is also in the ISO 11240:2012 standard. UCUM is also one of the designated standards in ONC’s USCDI.