Personal Item vs Carry On Bag and What Each Costs

On a budget carrier the personal item is free and the carry-on is not. On Frontier the difference is a bag six inches longer, two wider and two deeper, and $25 to $79 bought online according to KAYAK. For a week away, a traveler who can fit everything into 18 x 14 x 8 inches keeps up to about $158 of the flight budget. A traveler who cannot should buy the carry-on at booking and never at the gate, where KAYAK puts the charge near $100.

The choice therefore comes down to two things: how much the trip weighs in volume, and when the decision gets made. The second matters more than most travelers expect. The bag itself is cheap. Deciding late is what costs money.

Frontier's bag options page includes one personal item on every fare, up to 18 x 14 x 8 inches and 35 lbs, provided it fits under the seat. Spirit used the same dimensions before it ceased operations on May 2, 2026, and KAYAK notes that bags which passed Spirit's sizer should pass Frontier's, which matters now that Frontier has absorbed many of Spirit's routes. Ryanair's equivalent is 40 x 30 x 20 cm, free on every fare including Basic, per its help center bag policy.

The weakness is the size, and it is less forgiving than it was. National Traveller reports that since January 1, 2026, US airlines have measured bags with sizers that count wheels, handles, external pockets and straps. A bag that fails the gate sizer is no longer free. On Frontier it becomes a gate-priced carry-on, which is the most expensive way to own the larger allowance. The weight limit, by contrast, is generous: 35 lbs is more than most travelers can pack into 2,016 cubic inches.

The personal item costs nothing and suits anyone whose week of clothes fits in a small backpack that has been measured at home, with straps and pockets included.

Frontier's carry-on is large by any standard. At 24 x 16 x 10 inches it exceeds the 22 x 14 x 9 inches that Capital One describes as the most common airline maximum, and it offers nearly twice the box volume of the personal item. It carries the same 35 lb cap. It is not included on Basic fares, and Frontier states that its price rises the later it is bought: cheapest at initial booking, dearer at online check-in, dearest at the counter or gate. KAYAK puts the online range at $25 to $79 and the gate charge around $100. Frontier also sells a Board First add-on to guarantee bin space, which means the carry-on fee alone does not promise a spot overhead.

Ryanair follows the same pattern in euros. The Priority & 2 Cabin Bags add-on cost €/£12.49 to €/£36 online at booking and €/£19.99 to €/£45.50 at the airport, according to its fees page as checked on September 1, 2026. A non-compliant bag moved to the hold costs €/£69.99.

The carry-on suits travelers whose trip does not fit under a seat, and only when it is bought during booking.

A week away means two flights. KAYAK does not say whether Frontier's $25 to $79 applies per flight. If each leg is priced separately, as SendMyBag reports for Ryanair's cabin bag, the round-trip arithmetic is as follows:

• Frontier, personal item only: $0.
• Frontier, carry-on bought at booking: $50 to $158.
• Frontier, carry-on paid at the gate both ways: about $200.
• Ryanair, Priority & 2 Cabin Bags online both ways: €/£24.98 to €/£72.
• Ryanair, same add-on at the airport both ways: €/£39.98 to €/£91.

For a couple, double every line. Two Frontier carry-ons bought at booking come to $100 to $316, and that can be the difference between a hostel and a private room for several nights. The spread within each range is also a fact worth using. The fee moves by route and date, so the true cost of a fare is only known once the bag is priced for that specific flight.

That pricing has become harder to find in the US. DeepArrival reports that a Department of Transportation rule effective July 2, 2026 removed the requirement to show carry-on fees when fares first appear in search results. Airlines must still publish them on their own sites. Anyone comparing fares across airlines now has to add the bag price by hand.

The brief for this page asked about United's and American's basic economy fares as well. None of the sources available here publishes either airline's basic economy personal item size or carry-on terms. National Traveller reports only that American, Delta and United have deployed new measuring equipment. Travelers on those fares should read the airline's own baggage page before booking, because Capital One notes that personal item limits vary between airlines, from about 17 x 10 x 9 inches to 18.5 x 8.5 x 13.5 inches.

The strongest objection to going personal-item-only is that a cheap fare plus a carry-on can still lose to a legacy fare with the bag included. Which? found exactly that on London to Malaga, where British Airways cost £146.28 against £243.59 for Ryanair with a cabin bag added. The objection is sound, but it concerns which airline to choose rather than which bag. It strengthens the case for pricing the bag at booking, since that is the only moment both comparisons can be made. A traveler who packs light is not exposed to it at all.

Travelers who can fit a week into 18 x 14 x 8 inches, measured with every strap and pocket, should fly personal-item-only and keep the $50 to $158 a Frontier round trip would otherwise cost. Travelers who cannot should add the carry-on while booking, compare that total against a legacy fare that includes a bag, and treat the gate price as a penalty, not an option. The bag that most often costs about $100 is a free personal item that fails the gate sizer.

For Europe the calculation has an end date. The EU approved a free personal item for every passenger in July 2026, taking effect in 2027, and Aviation Business News reports that the rule also covers a free 7 kg wheeled cabin bag. The mandated personal item is 40 x 30 x 15 cm, five centimeters shallower than Ryanair's current allowance, so a bag bought for today's limit may not fit next year's. Measure the depth before buying anything.