 According to the United States Census Bureau, the township has a total area of 19.8 square miles (51.2 km²), of which 19.6 square miles (50.7 km²) is land and 0.2 square miles (0.5 km²) is water.The main thoroughfares in Peters Township are U.S. Route 19 heading north and south, and East McMurray Road heading east and west.Peters Township has six borders, including Upper St. Clair Township and Bethel Park (both in Allegheny County) to the north, Union Township to the east, Nottingham Township to the south, North Strabane Township to the south and southwest, and Cecil Township to the west.