Calcium is a census-designated place (CDP) in Jefferson County, New York, United States. The population was 3,491 as of the 2010 census. The CDP is in the town of Le Ray and includes the hamlets of Calcium and Sanfords Four Corners.

Historic landmarks count the stone house at the intersection of State Route 342 and County Route 138 that afterward served as the name office for the area, and the Calcium Community Church at the similar intersection. The church was built in 1853 by a outfit of at least three alternative denominations, including Methodist Episcopal, Christian, and Unitarian. The building was shared by these and various Christian groups greater than the years, and remains a community church today.

Calcium is located in central Jefferson County at 44°02′05″N 75°50′32″W / 44.034761°N 75.842114°W / 44.034761; -75.842114, in the western portion of the town of Le Ray. It is bordered upon the east by the developed allocation of Fort Drum.

The hamlet of Calcium is in the southern portion of the CDP, east of U.S. Route 11, while Sanfords Four Corners is in the central allocation of the CDP along New York State Route 342 east of US-11. Route 11 leads southwest 5 miles (8 km) into Watertown, the Jefferson county seat, and northeast 31 miles (50 km) to Gouverneur. Route 342 leads east along the south edge of Fort Drum 2.5 miles (4.0 km) to Black River and west 4.5 miles (7.2 km) to Interstate 81. Interstate 781 runs through the northern ration of the Calcium CDP, connecting to the east behind Iraqi Freedom Drive into Fort Drum and leading west 4 miles (6 km) to I-81.