Sulphur is located near the center of Calcasieu Parish. The city lies on Interstate 10 between the towns of Vinton and Westlake, approximately east of the Texas border. The city of Lake Charles is to the east. U.S. Route 90 passes through the center of Sulphur as Napoleon Street. Access from I-10 is via exits 20, 21, 23, and 26. According to the United States Census Bureau, the city has a total area of , all land.
