If both of Earth’s ice caps melted entirely, how much land would be engulfed in the resulting overflow?
Not nearly as much as the film “Waterworld” would make you believe.
Although estimates vary, one estimate is that, if the Antarctic icecap were to melt entirely, mean sea level would rise about 73 meters (240 ft). If Greenland melted as well, there would be a rise of an additional 7 meters (23 ft). So lets say about 80 m (260 ft) or so.
It should be pointed out that not even the most extreme global warming predictions suggest anything like this degree of melting within the next few centuries.
One of the reasons the estimates vary is that the extent to which the ice sheets have depressed the land under them, and raised the land around them is not well known, nor is the rate at which isostacy will be restored once the glaciers melt.