The U.K. pound coin weighs 9.5 grams as of 2014. Cost and the need to allow for higher denomination coins were the main considerations in deciding the weight of the pound coin, according to the Royal Mint.
The pound coin has a diameter of 22.5 millimeters, and at 3.15 millimeters, it is thicker than other U.K. coins. It is 70 percent copper, 24.5 percent zinc and 5.5 percent nickel. The coin was first introduced in 1983 as a replacement for the pound banknote due to a general decline in purchasing power, which made the coin more appropriate for the £1 unit of currency. In March 2014, the U.K. government announced plans to replace the round pound coin with a 12-sided coin of about the same size in 2017.