Frontier and Allegiant Personal Item Size, Plus Spirit's Old Limit
Frontier and Allegiant both give every fare one free personal item of 18 x 14 x 8 inches, measured with handles, wheels and straps on. The bag that flies free is the packed one that drops into the under-seat sizer. The number printed on its hangtag decides nothing at the gate.
Spirit used the same box until it stopped flying on 2 May 2026, so a "fits Spirit" listing now tells you only that the bag was cut to 18 x 14 x 8. We reread Frontier's bag options page and Allegiant's baggage page before this guide went live. United, JetBlue, Delta and the other majors sit side by side in our personal item bag comparison. Frontier and Allegiant print the box in different orders, count different attachments and handle a failed sizer differently.
Buying one? Personal Item Bag Size: Under-Seat Rules by Airline
The live 18 x 14 x 8 box
Both carriers print the same three numbers. They write them in a different order, and only Frontier publishes a weight.
| Airline | Personal item as printed | What counts | Weight | When it's checked | If it doesn't fit | Paid carry-on |
|---|---|---|---|---|---|---|
| Frontier | 18 x 14 x 8 in. Its help center writes 14 in H x 18 in W x 8 in D | Handles, wheels, straps | 35 lb | During boarding | Additional charge | 24 x 16 x 10 in, 35 lb |
| Allegiant | 8 x 14 x 18 in (20 x 35 x 45 cm) | Wheels, pockets, handles, decorations | None published | May be verified before boarding | Treated as a carry-on, fees apply | 10 x 16 x 22 in (25 x 40 x 55 cm) |
A packed bag 14 inches tall, 18 inches wide and 8 inches deep, handles included, passes both. Every other carrier we track, with the date we last read each one, is on the luggage size chart.
Frontier: 18 x 14 x 8, 35 lb, checked at boarding
Frontier's bag options page sets the personal item at 18 in by 14 in by 8 in and up to 35 lb, including handles, wheels and straps. One per passenger, per direction, comes with every ticket, and it has to fit under the seat in front of you. The page's examples are purses, small backpacks and laptop bags.
Frontier's help-center article What are the sizes and weight limits for bags? writes the same box as 14" H x 18" W x 8" D. Height is 14 inches there. Pack a bag to stand 18 inches tall and it can stop at a sizer opening that's 14 inches high, even though every number on its hangtag matches.
Frontier says personal-item size is checked during boarding and that items larger than the allowed dimensions are subject to an additional charge. The bag options page doesn't publish one flat gate price. Bag prices vary with your travel dates and when you buy, and Frontier's help center says airport prices are typically higher, so run your route through Frontier's bag price checker before you fly.
The 35-pound cap rarely touches a soft backpack. It can catch a wheeled under-seat case packed with books, cables or camera gear, so weigh that one at home.
The paid carry-on is 24 x 16 x 10 inches, also 35 lb with handles, wheels and straps. The Economy, Premium and Business bundles include it, and so do Elite Gold, Platinum and Diamond status for the member. A basic ticket doesn't. Coats, canes, crutches, portable oxygen concentrators and assistive devices are exempt from carry-on charges. A standard checked bag is a separate allowance: 62 linear inches and up to 40 lb.
Allegiant: 8 x 14 x 18, or it becomes a carry-on
Allegiant prints the personal item as 8 in. x 14 in. x 18 in. (20 cm x 35 cm x 45 cm). Read largest side first, that's 18 x 14 x 8. Depth leads because 8 inches is the squeeze under the seat. Every passenger gets one free, and the baggage page's examples are a purse, a briefcase, a laptop and a camera case.
The bag has to sit completely underneath the seat in front of you. Allegiant's baggage page says a personal item that doesn't fit completely under a seat may be considered a carry-on bag and charged accordingly, and that airport bag fees apply to oversized personal items. The baggage page doesn't print those fees. If the bag is borderline, price Allegiant's carry-on when you book rather than at the gate.
Measure wheels, pockets, handles and decorations. Allegiant names all four. A stuffed front pocket counts, and so does a dangling strap or a bulky patch. Cabin bags "may be verified prior to boarding."
The paid overhead bag is 10 in. x 16 in. x 22 in. (25 x 40 x 55 cm), or 22 x 16 x 10 largest first. No fare includes it for free. It's 2 inches shorter than Frontier's paid carry-on, so a 24-inch roller sized for Frontier is too tall for Allegiant even when the personal item matches.
Some roundups still quote Allegiant's personal item at 16 x 15 x 7 inches. Allegiant's baggage page publishes 8 x 14 x 18. Pack to that.
What Spirit used before it stopped flying
Spirit began an orderly wind-down on 2 May 2026, cancelled all flights and told guests not to go to the airport, according to its wind-down announcement. Its last published personal item was 18 x 14 x 8 inches, the same box Frontier and Allegiant publish now. Read a "fits Spirit" listing as an 18 x 14 x 8 claim and check it against the carrier on your ticket.
How to measure a packed personal item for a sizer
A sizer is a rigid frame, and it only ever meets the packed bag. Measure that.
Stand the bag the way it will sit under the seat. Measure height at the highest point, including a grab handle that sticks up. Measure width across the fullest side pocket. Measure depth with the back panel against a wall and the front left unsquashed. Stow the straps first, because Allegiant counts anything that hangs and a loose strap snags a Frontier frame too. Our step-by-step for packs is in how to measure a backpack for airlines.
A cardboard box makes a fair home check. Cut an opening 14 inches high and 18 inches wide, and mark a depth line 8 inches back. If the packed bag needs a shove at home, it'll need one at the gate.
Wheeled under-seat cases add height at the wheels. The tape method for a standing suitcase is on how to measure luggage.
Why a labeled 18 x 14 x 8 bag still fails
Retail listings often quote the shell rather than the outside. A grab handle, a trolley sleeve or a stuffed front pocket can add the inch that stops the bag at the lip of the frame. Soft nylon gives a little, then springs back. A hardside cut to the exact box has no give at all.
Leave expansion zips closed. How we handle listings that leave out the outside measurement is explained on how we measure.
One bag for both carriers
If your trips mix Frontier and Allegiant, size the under-seat bag to 14 inches tall, 18 wide and 8 deep, packed, and keep it under 35 lb for Frontier. For a paid overhead bag on both, size to Allegiant's 22 x 16 x 10, because Frontier's 24 x 16 x 10 is the roomier of the two.
That same 18 x 14 x 8 personal item runs too large on some major airlines, United among them, so check the personal item bag table before you carry it onto another carrier.
Bags cut to 18 x 14 x 8
Our shortlist of packs cut to this box is on personal item backpacks.
FAQ
What was Spirit Airlines personal item size?
18 x 14 x 8 inches, on its last published contract of carriage. Spirit stopped flying on 2 May 2026, so that box is historical. Frontier and Allegiant still publish the same size.
What is Frontier Airlines personal item size?
18 x 14 x 8 inches, including handles, wheels, and straps, and up to 35 lb. Frontier's FAQ writes the same box as 14 in high by 18 in wide by 8 in deep. One personal item per passenger, per direction, is included on every fare. Size is checked during boarding.
What is Allegiant Air personal item size?
8 x 14 x 18 inches (20 x 35 x 45 cm) as Allegiant prints it, which is 18 x 14 x 8 with depth first. Wheels, pockets, handles, and decorations count. Stow it all the way under the seat in front of you. One item is free on every fare.
Does Allegiant still use 16 x 15 x 7 inches?
No. That figure still circulates on third-party roundups. Allegiant's baggage page publishes 8 x 14 x 18 inches. Pack the bag to that box.
Do handles and wheels count on Frontier and Allegiant?
Yes. Frontier names handles, wheels, and straps. Allegiant names wheels, pockets, handles, and decorations. Measure the packed outside of the bag.
Does Frontier weigh a personal item?
Frontier publishes 35 lb for the personal item and for the paid carry-on. A typical under-seat pack will not get there. A wheeled mini-case full of dense gear can. Weigh that one.
What happens if the bag does not fit the sizer?
Frontier says items larger than the allowed dimensions are subject to an extra charge, checked at boarding. Allegiant may reclass an oversize personal item as a carry-on and collect the carry-on fee, or assess an at-airport oversize fee. Buy the cabin bag before you reach the gate if you already know it will not drop in.
Can you bring a carry-on plus a personal item on Frontier or Allegiant?
Yes, if you pay for the carry-on or your bundle already includes it. The personal item is the only free cabin bag on a basic fare for both. Frontier's paid cabin bag is 24 x 16 x 10. Allegiant's is 22 x 16 x 10.
Filed in Travel Tips