All U.S. pennies (1-cent pieces) minted since 1982 weigh either 2.5 grams (0.088 ounces) or 3.11 grams (0.109). The 2.5 grams Lincoln Penny is composed of brass (95% copper, 5% zinc), while the 3.11 grams Union Shield is composed of copper-plated zinc (97.5% zinc, 2.5% copper). All current U.S. pennies have a diameter of 19.05 mm, a thickness of 1.52 mm, and are composed primarily of zinc (97.5%) with a copper plating (2.5%).
The U.S. government first proposed the penny in Coinage Act of 1792. Pennies went into production for the first time in 1793 with a 100% copper penny that weighed a hefty 13.48 grams (0.475 ounces). From 1795 to 1857, the copper penny was reduced in size with a new weight of 10.89 grams (0.384 ounces). From 1856 to 1864, the U.S. reduced the composition of the penny for the first time, reducing the amount of copper to 88% and included 12% nickel, for a new weight of 4.67 grams (0.164 ounces).
From 1864 to 1942, the U.S. minted a newly redesigned penny that weighed 3.11 grams (0.109 ounces) and was composed primarily of bronze (95% copper, 5% zinc and tin). In 1943, the U.S. printed zinc-coated steel penny for just one year. The steel penny weighed 2.72 grams (0.095 ounces). From 1944 to 1981, the U.S. minted several coins composed primarily of copper (95%) and zinc (5%), that weighed 3.11 grams (0.109 ounces), with a bronze penny minted from 1947 to 1962.