Normal pressure hydrocephalus is a treatable dementia often misdiagnosed as Alzheimer’s Disease. Callosal angle measurement distinguish normal pressure hydrocephalus from other dementias but measurements are time-consuming and subjective. Therefore, we developed an algorithm for automatic callosal angle measurement and calculated callosal angles for 4,980 T1-weighted MRIs from databases of patients with purportedly healthy aging brains or Alzheimer’s. Based on the published guidelines, 1.8-4.3% of exams in these databases indicate patients likely have normal pressure hydrocephalus and thus a treatable form of dementia. Our automatic measurement of the callosal angle biomarker can rapidly and objectively screen patients for normal pressure hydrocephalus.