A rough estimate of the total playable/traversable surface area of Dwarrows.
Map of the Dwarrows Overworld Area
Cats provide distances, in meters, in which sprites are detected. Three cats provided a total of 316 m of this.
I moved Horbir around until going North one step stopped showing the sprite on the map, then moved back South until it reappeared. After zooming in and out a bunch of times, and scaling, here’s the result.
This excludes internal areas like Trials and is an estimate. Notice how some squares overlap slightly, or go a bit over the edge, or miss some small gaps. This, probably, all evens out in the end, anyway.
TL;DR: The map’s 1,062.5 km².
Click the image to see the map.