How big is a dreadnought?

The original HMS Dreadnought of 1905 had a displacement of over 18,000 tons which made it a large ship for the time, but its length was comparable to a destroyer of today. Other countries began building their own dreadnoughts, many of them larger and more imposing. Spain, an empire in decline, built the smallest dreadnoughts, but any of the dreadnoughts would be dwarfed by a World War 2 battleship.