1/2 the depth of one rabbet on the stiles
1/4 on the rails3/8" rabbets will require that the panel be 3/16" short of flush fitting assuming trditional vertical grain orientation. As there is less expansion with the grain, 1/8" clearance should be sufficient on the rails of your doors.That also translates to 3/32" shaved off each side of a panel set in 3/8" rabbets.If that is confusing: If your total opening to the full depth of the rabbets in the stiles and rails is 18" by 34" (assuming a square panel which you likely will not be building), the panel would be 17-13/16" by 33-7/8".
1/4 on the rails3/8" rabbets will require that the panel be 3/16" short of flush fitting assuming trditional vertical grain orientation. As there is less expansion with the grain, 1/8" clearance should be sufficient on the rails of your doors.That also translates to 3/32" shaved off each side of a panel set in 3/8" rabbets.If that is confusing: If your total opening to the full depth of the rabbets in the stiles and rails is 18" by 34" (assuming a square panel which you likely will not be building), the panel would be 17-13/16" by 33-7/8".