Spirit's personal item can be up to 18 x 14 x 8 inches (45 x 35 x 20 cm), handles and wheels included. It's free on every fare and has to fit under the seat in front of you, while a carry-on (up to 22 x 18 x 10 inches) costs extra on Spirit's Value fare.
That's from Spirit's own help pages, checked in October 2026. A small backpack counts, as long as it stays inside that box. If you're shopping for one bag that does the job, the 17-inch Air Pro compression backpack is within Spirit's limit by its published dimensions, and the 19-inch version is not.
What are Spirit's bag size limits in 2026?
Spirit sells three travel options: Value, Premium Economy and Spirit First. The personal item is the same on all of them. What changes is whether a carry-on or checked bag comes with the ticket.
| Bag | Maximum size | Value fare | Premium Economy | Spirit First |
|---|---|---|---|---|
| Personal item | 18 x 14 x 8 in (45 x 35 x 20 cm) | Free | Free | Free |
| Carry-on bag | 22 x 18 x 10 in (56 x 46 x 25 cm) | Paid extra | Included (space permitting) | Included |
| Checked bag | 62 linear inches (158 cm), up to 50 lb | Paid extra | Paid extra | One included |
Source: Spirit Bag Info and Spirit Travel Options, both checked October 2026. Spirit doesn't list a weight limit for the personal item on that page.
So on a Value fare, the personal item is your only free bag. That's why the 8-inch depth gets so much attention.
What counts as a personal item on Spirit?
Spirit gives a purse, a small backpack and a laptop bag as examples. You get one. A second personal item, or anything bigger than the limit, is charged as a carry-on.
A few things don't count against you. Spirit's page lists umbrellas, cameras, infant diaper bags, assistive devices, outer garments such as a coat, hat or wrap, reading material and food for the flight as allowed at no charge (checked October 21, 2026).
If you carry a purse and a backpack, put the purse inside the backpack before you reach the gate. Two items is the most common way people end up paying.
Does Spirit use a sizer at the gate?
Spirit's own wording is that your personal item must fit entirely in the "smaller sizer bin," handles and wheels included. That's the test the policy is written around.
The help page doesn't say where the sizer stands or when staff use it. Plan as if your bag will go in it. A bag that's 18 x 14 x 8 when empty can be deeper than 8 inches once it's packed round, and depth is usually what stops a soft backpack from sliding in.
Is a backpack a personal item on Spirit?
Yes. "Small backpack" is one of Spirit's own examples. The bag has to meet 18 x 14 x 8 inches with everything attached, so measure it packed, not empty, and include the side pockets.
Water bottles are a common surprise. A full bottle in a side pocket can add an inch or more to the width.
How much can you pack in an 18 x 14 x 8 bag for 3, 5 or 7 days?
The box itself is 2,016 cubic inches, about 33 liters. No bag uses all of it, because the walls, straps and padding take some room. What fits depends far more on what you pack than on the bag.
3 days
Most people manage a weekend in a regular personal-item backpack. Wear your heaviest shoes and jacket on the plane, bring one extra pair of pants, and keep toiletries in travel sizes.
5 days
This is where planning starts to matter. Pick tops and bottoms that all go together so you can repeat pieces, and roll soft items tightly. Leave a second pair of shoes at home if you can.
7 days
A week in one under-seat bag usually means one of two things: a plan to wash a few things midway, or a way to take up less space. Compression packing cubes squeeze clothes, and a vacuum compartment pulls the air out of them.
Neither changes the weight, and both still have to fit inside the same 18 x 14 x 8 box.
For a longer trip, our guide on how to pack 2 weeks in a carry-on goes through a full list.
Which Air Pro size fits Spirit's personal item limit?
This is a comparison of published numbers. We have not tested either bag in a Spirit sizer.
| Air Pro size | Published dimensions | Spirit personal item (18 x 14 x 8 in) | Spirit carry-on (22 x 18 x 10 in) |
|---|---|---|---|
| 17-inch | 17 x 12.6 x 6 to 8 in (43 x 32 x 15 to 20 cm) | Within the limit, with 1 inch to spare on length and 1.4 inches on width | Within the limit |
| 19-inch | 19 x 12.6 x 6 to 8 in (49 x 32 x 15 to 20 cm) | Over the limit by 1 inch of length | Within the limit (paid extra on a Value fare) |
The 17-inch depth tops out at 8 inches when fully expanded, which matches Spirit's depth limit exactly. Keep the front pocket from bulging and the bottle pocket from sticking out, and it stays inside the numbers.
The 19-inch is a carry-on bag on Spirit. If you already pay for a carry-on, or you book Premium Economy or Spirit First, it works there. On a Value fare with no carry-on, choose the 17-inch.
Both sizes start at $149, with the rechargeable pump included and a 90-day return window.
Downsides to know before you rely on compression
Vacuum compression makes clothes smaller, not lighter, and the bag itself weighs 3.5 to 4 pounds empty. Linen and some cotton shirts come out creased.
You need the pump to reseal the bag for the flight home. And because the clothes sit in one sealed compartment, grabbing one shirt means opening all of it.
Who this isn't for
If you fly Spirit only once in a while and a Premium Economy fare already includes your carry-on, a compression backpack solves a problem you don't have. The same goes if you need wheels, or if you'd rather not deal with a pump at the end of a trip.
See how Spirit compares with other carriers in our personal item size by airline chart, or read the Frontier personal item rules, which use the same 18 x 14 x 8 box with a few differences.
For the general rules across airlines, see what counts as a personal item, and our guide to fitting a vacuum backpack into 18 x 14 x 8 explains how to measure a packed bag.
FAQ
Is Spirit strict about personal item size?
Spirit's policy says the item must fit entirely in the smaller sizer bin, handles and wheels included. We can't tell you how often agents check. Packing to the exact limit is the safest plan.
Does Spirit have a weight limit for personal items?
Spirit's Bag Info page lists no weight limit for the personal item as of October 2026. Checked bags are limited to 50 pounds.
Can I bring a backpack and a purse on Spirit for free?
Only one personal item is free. A second item is charged as a carry-on, so put the purse inside the backpack.
Is Spirit's personal item size the same as Frontier's?
Yes, both are 18 x 14 x 8 inches. Frontier adds a 35-pound weight limit and counts straps in the measurement.
If you want one bag that fits Spirit's free allowance, start with the 17-inch on the Air Pro page.