British decimal general circulation coins are dimensioned as follows:

1 Penny (from 1968 - 1991) 20.32 mm diameter, 1.52 mm thick, weigh 3.56 grams and are made from 97% copper, 2.5% zinc and 0.5% tin. The edge is plain.

1 Penny (from 1992) 20.32 mm diameter, 1.65 mm thick, weigh 3.56 grams and are made from copper plated steel. The edge is plain.

2 Pence (from 1971 - 1991) 25.9 mm diameter, 1.85 mm thick, weigh 7.12 grams and are made from 97% copper, 2.5% zinc and 0.5% tin. The edge is plain.

2 Pence (from 1992) 25.9 mm diameter, 2.03 mm thick, weigh 7.12 grams and are made from copper plated steel. The edge is plain.

5 Pence (from 1990 - 2011) 18 mm diameter, 1.7 mm thick, weigh 3.25 grams and are made from 75% copper and 25% nickel. The edge is milled.

5 Pence (from 2011) 18 mm diameter, 1.7 mm thick, weigh 3.25 grams and are made from nickel plated steel. The edge is milled.

10 Pence (from 1992 - 2011) 24.5 mm diameter, 1.85 mm thick, weigh 6.5 grams and are made from 75% copper and 25% nickel. The edge is milled.

10 Pence (from 2011) 24.5 mm diameter, 1.85 mm thick, weigh 6.5 grams and are made from nickel plated steel. The edge is milled.

20 Pence (from 1982) 21.4 mm diameter, 1.7 mm thick, weigh 5 grams and are made from 84% copper and 16% nickel, and are seven sided or heptagonal. The edge is plain.

25 Pence (from 1972 - 1981) 38.61 mm diameter, 2.5 mm thick, weigh 28.28 grams and are made from 75% copper and 25% nickel. The edge is milled. During their period of issue, they were referred to as a Crown due to them being of the same dimensions as the pre-decimal Crown coin. These coins were discontinued from 1982 but remain legal tender. Circulation of these coins is uncommon.

50 Pence (from 1997) 27.3 mm diameter, 1.78 mm thick, weigh 8 grams and are made from 75% copper and 25% nickel, and are seven sided or heptagonal. The edge is plain.

1 Pound (from 1983) 22.5 mm diameter, 3.15 mm thick, weigh 9.5 grams and are made from 70% copper, 24.5% zinc and 5.5% nickel. The edge is milled with incuse lettering or ornamentation.

2 Pound (from 1986 -1996) 28.4 mm diameter, 3.1 mm thick, weigh 15.98 grams and are made from 70% copper, 24.5% zinc and 5.5% nickel. The edge is milled with incuse lettering. Due to them being issued as commemoratives, circulation of these coins is uncommon.

2 Pound (from 1997) 28.4 mm diameter, 2.5 mm thick, weigh 12 grams and are bimetal made from 76% copper, 20% zinc and 4% nickel in the outer ring, and the centre is 25% nickel and 75% copper. The edge is milled with incuse lettering.

5 Pound (from 1990) 38.61 mm diameter, 2.89 mm thick, weigh 28.28 grams and are made from 75% copper and 25% nickel. The edge is milled. Intended as a souvenir or collectible, but occasionally seen in circulation. These coins are now referred to as a Crown due to them being of the same dimensions as the pre-decimal Crown coin.

The following are specifications of British decimal coins which have been demonetised and are no longer legal tender. Unless they are uncirculated or Proof, they have minimal collector value.

Half Penny (from 1971 - 1984) 17.14 mm diameter, 1 mm thick, weigh 1.78 grams and are made from 97% copper. The edge is plain.

5 Pence (from 1968 - 1989) 23.59 mm diameter, weigh 3.25 grams and are made from 75% copper and 25% nickel. The edge is milled.

10 Pence (from 1968 - 1992) 28.5 mm diameter, weigh 11.31 grams and are made from 75% copper and 25% nickel. The edge is milled.

50 Pence (from 1969 - 1996) 30 mm diameter, 1.78 mm thick, weigh 13.5 grams and are made from 75% copper and 25% nickel, and are seven sided or heptagonal. The edge is plain.