Spirit allows passengers one free personal item, such as a purse, laptop bag, or small backpack. Your personal item must be small enough to store under the seat in front of you. Spirit requires personal items not to exceed 18 x 14 x 8 inches, including handles and wheels.

Yes, a backpack is considered a personal item on Spirit Airlines as long as it fits entirely within the "sizer box" at the gate, which measures 18 x 14 x 8 inches (45 x 35 x 20 cm). This personal item is the only piece of luggage included for free with a standard Spirit "Bare Fare." If your backpack is a standard daypack or school bag, it will almost certainly fit under the seat in front of you and pass as a personal item. However, if you are using a large 40-liter hiking pack or a bulky "travel backpack," it may exceed these dimensions and be reclassified as a carry-on bag, which carries a steep fee—often $65 or more if paid at the gate. In 2026, Spirit agents are increasingly vigilant about measuring bags, so it is crucial to ensure your backpack isn't "overstuffed" to the point where it won't slide into the metal sizer. If you can't fit your bag under the seat, you will be required to pay the carry-on fee and use the overhead bin.