Joists and rafter spans for common loading conditions can be determined.
The American Wood Council (AWC) Span Calculator for Wood Joists and Rafters (Span Calc) performs calculations for all species and grades of commercially available softwood and hardwood lumber as found in the 2018 National Design Specification® (NDS®) for Wood Construction. Calculator for Wood Joists + Rafters for all species and grades of commercially available softwood and hardwood lumber as found in the 2018 National Design Specification®