Grind them up and fit much more in the box
You’re onto something here. The original author didn’t consider that doughnuts are three dimensional and only calculated based on a two-dimensional doughnut shape. It would vary by exactly how the square vs. round doughnuts are shaped, but even with the same sized holes as his measurements, it’s possible for three-dimensional square doughnuts to be more than 27% bigger due to the squared edge.
Assuming the round doughnuts are exactly round on their axis (I don’t even know how you accurately describe the circumference of the side of the doughnut), and the square doughnuts are exactly square/cubed, you can:
- Learn trig (?) and calculate the three-dimensional differential, way above my pay grade.
- Spray the doughnuts so they’re sealed and don’t absorb water, and see how much water they each displace to figure out their mass
- Follow etech0’s example and crumb them up, and compare the crumb masses for an approximate differential