<p>The transport of water at the nanoscale is fundamental to advancements in nanofluidics, membrane technology, and biological systems. While numerous studies have investigated the one-dimensional diffusion of water in carbon nanotubes (CNTs), its viscosity remains underreported. Experimental measurements of viscosity at this scale are challenging, but molecular dynamics simulations offer a viable alternative for predicting the viscosity of cylindrically confined water. Various methods have been employed for this purpose; however, their limitations raise questions about the accuracy of the predicted values. Our group has developed a novel approach, the Jump-corrected confined Stokes–Einstein (JCSE) method, based on the confined Stokes–Einstein equation, to estimate the viscosity of water within cylindrical nanopores. This technique is particularly promising because it accounts for the breakdown of the Stokes–Einstein relation in both confined and supercooled water, enhancing the reliability of viscosity predictions. In this short perspective, we introduce the JC-CSE method and its application to supercooled water confined in hydrophobic and superhydrophobic CNTs. Additionally, we rationalize viscosity trends using hydrogen-bond analysis. Finally, we provide a brief outlook on the broader applicability of this method to other confined liquids.</p> Graphical abstract <p>This figure illustrates approaches to determining the viscosity under confinement. Traditional Green–Kubo relations are often inadequate, while the confined Stokes–Einstein relation offers alternatives. The Jump-corrected Confined Stokes–Einstein (JCSE) equation introduces corrections for molecular jumps and confinement effects, relating viscosity to diffusion, temperature, and confinement length scale, improving accuracy in nanoscale systems.</p> <p></p>