81.915 cm x 50.8 cm,and the base does seem to slope at least a tiny bit so not quite!It really isn't substantially bigger,only about 25 square inches.Enough for an extra toy maybe,but not enough to make much of a difference.
I know that the size is popular for Syrians,but that doesn't mean it is the most appropriate or necessarily a good fit.
I've known of many Syrians who have done terribly in that size range,so it isn't necessarily just an opinion.Regardless of enrichment and other things,a lot of hamsters would persist in exhibiting the same exact stereotypic behavior(an indicator of boredom and poor habitat,in other words)and sadly a lot of the time most people don't want to blame it on the cage size.
Regardless,I don't necessarily think it should discourage purchasing of the cage where appropriate
For example,transitioning to a larger cage for Syrians or as a dwarf hamster cage or senior hamster cage as mentioned.