From the Boeing and Airbus websites.
The wingspan of the B747-400 is 64.44m going up to 69.8m on the 747-400 Stretch and the present length is 70.66m going up to 79.8m on the Stretch. The A380 will have a wingspan of 79.8m and a length of 73m. So you can see that although the wing span is considerably greater on the A380, 15.4m, the length is not that different. The major problem with the A380 will be finding somewhere to park the thing and maneouvering around airports. At most airports with two B747-400's next to each other there would only be about 10m between the wingtips. Two A380's won't fit on adjacent bays and in some places won't be able to pass each other on parallel taxiways.
The sites are:
http://www.boeing.com
http://www.airbus.com
[This message has been edited by Bullethead (edited 08 January 2001).]