For really quick lookups of NDL, I have a picture of the PADI RDP (DSAT-based) on my phone and much of it memorized. Most of the time, though, I dive more conservatively by using Buhlmann+GF (x/85).
The free/open source desktop version of Subsurface (Windows/Linux/Mac) has a comprehensive multi-level and repetitive dive planner. NDL mode will extend time at your last depth until the user-specified gas reserve is reached. Rock-Bottom/Min Gas reserve information is also provided. (The iOS/Android mobile version of Subsurface does not have a planner.) Buhlmann+GF and VPM-B algorithms supported.
For mobile (Android), I like "Diveplanner Tec & Rec". Free for single-gas, reasonable price for multi-gas. Has a grid layout for square profiles (NDL clearly visible) and a separate multi-level/repetitive planner. Another I like is TechDeco (free, square profile, multi-gas); pretty quick to twiddle the time to find the NDL if that's your desire. Both of these use the Buhlmann+GF algorithm.
The free/open source desktop version of Subsurface (Windows/Linux/Mac) has a comprehensive multi-level and repetitive dive planner. NDL mode will extend time at your last depth until the user-specified gas reserve is reached. Rock-Bottom/Min Gas reserve information is also provided. (The iOS/Android mobile version of Subsurface does not have a planner.) Buhlmann+GF and VPM-B algorithms supported.
For mobile (Android), I like "Diveplanner Tec & Rec". Free for single-gas, reasonable price for multi-gas. Has a grid layout for square profiles (NDL clearly visible) and a separate multi-level/repetitive planner. Another I like is TechDeco (free, square profile, multi-gas); pretty quick to twiddle the time to find the NDL if that's your desire. Both of these use the Buhlmann+GF algorithm.