Webiga Potomac wuxuu ku socdaa in ka badan 383 mayl ee Fairfax Stone, West Virginia ilaa Point Lookout, Maryland. Waxay saameyneysaa in ka badan 6 milyan oo qof oo ku nool meel ka mid ah Potomac, oo ah 14,670-kiilomitir oo dhul ah oo biyaha biyaha u soo baxaayo webiga. Khariidadani waxay muujinaysaa meesha ay ka socoto webiga iyo aagaggeeda biyaha ee ku saleysan dhowr gobol oo jiilaal ah oo ay ka mid yihiin Meelaha Appalachian, Ridge & Valleys, Blue Ridge, Piedmont, iyo Coastal Plain.
Dhismaha ugu weyn ee lagu daro dhamaan qaybaha waawayn ee isugu jira 12,878.8 miles oo ka dhigaya Webiga Potomac oo ah 21ka ugu weyn ee Maraykanka. Wareegyada ugu muhiimsan ee webiga Potomac waa Woqooyiga Laanta, Wabiga Savage, Koonfurta Laanta, Cacapon, Shenandoah, Antietam Creek, Wareegga Monocacy, iyo Webiga Anacostia. Potomacku wuxuu ku faafaa dhinaca galbeedka Chesapeake Bay .