The standard king-size bed dimensions are 76 inches wide by 80 inches long, or 193 by 203 centimeters. However, in the United States, there are two versions of the king-size bed. The California king-size bed is 72 inches wide and 84 inches long, or 183 by 213 centimeters.
These king-size dimensions give ample room for the average couple to lay down side by side without touching. This is the equivalent size of pushing together two twin-size mattresses. Most king-size beds use two twin box springs for support. Those who need extra length might consider the California king as an option.