At 13 minutes per pound, 21 x 13 = 273 minutes, or 4 hours 33 minutes. At 15 minutes per pound, it’s 315 minutes, or 5 hours 15 minutes. So, aim for a window between 4.5 and 5.5 hours—and start checking at the 4-hour mark.
Cornell Cooperative Extension | How to Cook a Thanksgiving Turkey
Pro tip: Let the turkey rest for 30 minutes after it comes out. The internal temperature will rise another 5-10°F (that’s called carryover cooking). And it gives you time to make gravy without a hot, frantic mess.
The Stuffing Situation
Don’t overstuff the cavity. The stuffing needs room to breathe and cook through. Loosely fill it—about ¾ cup of stuffing per pound of bird. For a 21 lb turkey, that’s roughly 15 cups of stuffing, but use your judgment.
And here’s the fun part: the stuffing must reach 165°F just like the breast. That’s non-negotiable. But hey, it’s the perfect excuse to eat a test spoonful of raw-ish breadcrumbs before baking. (I won’t tell.)
Cooking Times for a 22 lb Stuffed Turkey – THEKITCHENTODAY