When preparing a turkey, allow for approximately 3/4 cup of stuffing per pound of turkey. With a 20-pound turkey, 15 cups of stuffing are recommended.
When preparing the turkey, the stuffing should be added to the turkey right before roasting and shouldn't be packed too tightly. While preparing the stuffing ahead of time is acceptable, adding it to the turkey too far in advance of roasting can lead to potential unsafe cooking temperatures. This also applies if the turkey is packed too tightly, as stuffing expands in the turkey as it cooks and can prevent the turkey from cooking all the way through.