Borosilicate glasses have been in widespread use for over a century; however, a detailed understanding of the structural response to densification is still lacking. In this work, two commercial borosilicate glasses, viz., SCHOTT N-BK7 (R) (N-BK7) and Borofloat33 (R) (Boro33), are hot compressed up to 2 GPa with nitrogen gas, and the structural response to this densification is explored via B-11 solid-state nuclear magnetic resonance (NMR) spectroscopy and classical molecular dynamics (MD) simulations. The molar volume (V-m) of N-BK7 and Boro33 decreases similar to 5% and similar to 10%, respectively, as a result of hot compression at 2 GPa. The NMR results demonstrate the presence of three different types of fourfold coordinated boron species (B-[4]), which are confirmed in MD simulations to be B-1([4])(0B,4Si([4])), B-2([4])(1B([3]),3Si([4])), and B-3([4])(1B([4]),3Si([4])) (where subscripts represent different B-[4] types and brackets indicate the next nearest neighbors (NNN)). The NMR results also show that the fraction of B-[4] increases by similar to 13% in N-BK7 glass upon hot compression at 2 GPa via the trigonal boron to tetrahedral boron (B([3] )to B-[4]) conversion, while the fraction of B-[4] in Boro33 glass only increases by similar to 2% at the same pressure, despite the fact that the V-m decrease in N-BK7 is double that of Boro33. The MD simulations capture the experimental trends in B-[4] populations, despite an underestimation of the B-[4] increase of N-BK7 (only similar to 6%) at 2 GPa. Moreover, the MD simulations suggest that the V-m reduction is a linear function of bond angle change and the fraction of Si-O-Si and B-[4]-O-Si. The modifiers and boron coordination conversion also influence the volume densification of borosilicate glasses by increasing the difficulty of bond bending, decreasing the bond lengths, and increasing the population of B-[4]-O-Si linkages. Finally, the B-[4] to B-[4] conversion, that is, B-2([4])(1B([3]),3Si([4])) and B-3([4])(1B([4]),3Si([4])) to B1[4] (0B,4Si([4])), is observed in hot compressed N-BK7 and Boro33 from NMR and qualitatively confirmed in MD.