First, consider how and where you plan to use the pack. Are you aiming to day-hunt from your truck, so you only need to carry a few safety essentials and enough gear for field dressing an animal? Or are you considering a three-day trip on horseback to a remote cabin, or maybe a week-long backpack hunt in the mountains, requiring you to pack out any game you take?
Hunting pack capacities are generally measured in cubic inches, ranging from less than 1,000 to 6,000 or more. As a broad guideline, count on needing roughly 1,000 cubic inches for every day you’ll be in the field; the difference between a three- and six-day trip is primarily the amount of food you’ll need to bring. Err on the side of slightly too big, especially if the pack you select can be evenly compacted using compression straps. If you expect to carry out game, consider a pack that can accommodate a quarter.