Traveling with a duffel bag is one of the most convenient ways to transport your belongings when you’re on the go. But if you plan to take your duffel bag onto an airplane, it’s important to know what size and weight are allowed. Generally, airlines allow passengers to bring one carry-on item plus one personal item onboard for free. The largest duffel that can be considered a personal item is typically around 22 inches in length, 14 inches in width and 9 inches in depth—or 45 linear inches (length + width + height). Anything larger than this will likely have to be checked as luggage and may incur additional fees depending on the airline’s policy. It’s also important to note that different airlines might have slightly different restrictions for maximum size so make sure you check before packing up your duffel! Additionally, all bags should weigh less than 40 pounds since anything above that could result in an extra fee or even having items taken out of your bag altogether. With these guidelines in mind, travelers can confidently choose their ideal sized duffle without worrying about exceeding limits at the airport!