Allegiant's official baggage page lists one free personal item up to 18 × 14 × 8 inches that fits completely under the seat. A larger carry-on is a different product, with a 22 × 16 × 10 inch maximum and a charge unless the chosen bundle or purchase includes it. Measure the packed outside of the bag, including wheels, pockets and handles.
Free item or paid carry-on?
| Product | Published size | Price question |
|---|---|---|
| Personal item | 18 × 14 × 8 in | Included when it fits the underseat rule |
| Carry-on | 22 × 16 × 10 in | Check bundle or separate purchase price |
| Checked bag | Separate weight, size and booking rules | Do not infer from cabin dimensions |
An 18-inch backpack is not automatically a personal item if it is too deep after packing. Likewise, the word “weekender” does not decide which cabin product it is. Compare all three sides. A total linear measurement cannot replace Allegiant's box.
A packing example
Suppose a soft bag is 17 × 13 × 7 inches when empty and 18 × 14 × 9 inches after you add shoes. The packed depth exceeds the 8-inch personal-item side. Removing the shoes may restore underseat fit. If you instead use the bag as your carry-on, check the fare or bundle and buy the correct product before travel. Allegiant says airport prices are higher than advance bag reservations, but the exact charge must come from your itinerary.
Allegiant's current main baggage policy and its official contract identify the 18 × 14 × 8 inch box. An older popup about changed bag fees may show a different smaller personal-item figure; use the current policy and booking rather than a historical snippet. If two official pages appear to disagree for your ticket, keep screenshots and ask Allegiant which applies.
The personal item checker can compare dimensions. It cannot verify whether a particular bag will fit a specific aircraft seat or decide a dynamic gate charge. For a medical aid, infant item or pet carrier, read the separate official policy rather than treating it as an ordinary extra personal item.
Airline sources
Sources last checked 2026-10-31. Match the fare and flight in your booking before you pay or pack.