According to the United States Census Bureau, the Fredericksburg CDP has a total area of , all land. The community is drained by Deep Run and Beach Run, which join south of the town to form Elizabeth Run, a tributary of Little Swatara Creek and part of the Susquehanna River watershed.
aCCOrding to tHE United stAtes Census BurEaU, THe fredericKSBurg cdP haS a totaL area oF , aLl Land. the coMmunItY is DraIneD by deep rUn and beach run, WhicH join south Of THe town to form ElizAbEtH rUn, a Tributary of littlE swatarA CReeK aND PArt of the susquEhanna riVEr watershed.