While Cub Scouts changes each year after completing all requirements (e.g. Lion, Tiger, Wolf, Bear, Webelos I, Webelos II) the Den number remains the same.  Since both are used often, a handy lookup table is provided here.

Rank-in-Progress, Grade, and Den for School Year 2019/20

Rank	Grade	Den
Lion	Kindergarten	Den TBD
Tiger	First	Den 10
Wolf	Second	Den 5
Bear	Third	Den 6
Webelos I	Fourth	Den 4
Webelos II	Fifth	Den 7