The United States has five standard bed sizes: twin, full, queen, king and California king. The United Kingdom has four standard size: single, double, king and super king.
The United Kingdom's king size duvet is the same size as the United State's standard queen size duvet. Both are 88 x 86 inches, or 225 x 220 centimeters.
In the United States, all king size duvets are 102 x 86 inches, which is comparable to the UK super king size, which is 260 x 220 centimeters. The United States' California king size has no equivalent and is longer than it is wide at 114 x 106 inches, or 290 x 270 centimeters.
The European king size duvet is similar but not exactly the same as the UK king and US queen sizes. At 240 x 220 centimeters, the European king size is between the UK king and super king sizes. A super king size is also sold in Europe, and it is the same dimensions as its UK namesake. Australia has a different sizing standard, which falls between the US and UK king sizes. At 240 x 210 centimeters, the Australian king size is larger than the UK king but smaller than the US and European king sizes.