Alright, so I manually counted how tall the map of Hallownest is. From the bottom of the Abyss, to the Surface for both Dirtmouth and Hallownest Crown.
Remember that this is assumptions and probably not 100% accurate, but probably quite close to it.
Firstly, with these measurements I assumed that The Knight is around 5 cm tall. This is primarily based on the "Hornet can strike down enemies from 30 yards" and we see her Silksoar from the bottom of Moss Grotto to the Blasted Steps. After some calculations, this means that The Knight and Hornet would be around 5 and 7 cm respectively.
Secondly, I first measured the amount of The Knight from the bottom to the top of the map as you can see on the image.
Thirdly, this was all counted on the very convenient https://www.hallownest.net, where the map was very accurate and nice to work with.
Anyways, here's the results:
The bottom of the Birthplace to Dirtmouth is 605 The Knights tall
605 * 5 cm = 3025 cm, or 30,25 meters, or 99 feet and 3 inches OR the size of a 8 story building.
The bottom of the Birthplace to Hallownest Crown is 727 knights tall
727 * 5 cm = 3635 cm, or 36,35 meters, or 119 feet and 3 inches OR the size of a 10 story building.
Quite large compared to our size tbh.