Spirit Airlines is putting the squeeze on your personal item.

The discount carrier, which charges extra for basics ranging from a seat selection to a bottle of water, will tighten the dimensions of the item you’re allowed to carry on board for free.

Beginning Apr. 4, the pioneer of the Bare Fare is downsizing the dimensions of your personal item to 18-by-14-by-6 inches. Until then, you can live large and enjoy the roominess of an item measuring 16-by-14-by-12 inches.

Remember, that’s height-by-length-by-width. No moving those inches around. In terms of cubic inches, here’s how the new rule compares with the old rule for volume:

  • New personal item: 1,512 cubic inches.
  • Old personal item: 2,688 cubic inches.

Bulkier personal items will incur the cost of a carry-on bag.

Spirit sticks with strategy

Spirit doesn’t apologize for running a lean travel machine. That’s the whole idea. The airline describes its Bare Fare this way:

“Our fares are unbundled: no “free” bag, no “free” drink. From the start, it’s just your a** plus gas…and a personal item.”

Spirit continues to add flights and routes. The Florida-based airline operates more than 400 daily flights to more than 59 destinations in the United States, Latin America and the Caribbean.

To keep your travel costs low, it’s always best to book early—and remember to measure that personal item before heading to the airport.

United, American rethink personal items

Spirit isn’t the only airline creating a bit of turbulence for travelers.

United Airlines is introducing its Basic Economy fare to compete with discount carriers. Travelers who buy this fare—the lowest United offers—will be banned from using overhead-compartment space. They can bring a personal item on board, but it has to go under the seat. But watch those dimensions: 9-by-10-by-17 inches. That’s 1,530 cubic inches, 18 more than Spirit allows.

American Airlines is also introducing a basic-economy fare. Like United, American has made use of the overhead compartment forbidden. American ticket holders can bring a more spacious personal item. That’s 18-by-14-by-8 inches for a total of 2,016 cubic inches—best in class, but still fewer than Spirit’s pre-shrunk personal item.

United and American travelers with a budget ticket should be forewarned: Should a personal item exceed the prescribed dimensions, they will have to check the item at the gate for the usual $25 checked-bag fee, plus another $25 for handling.

Presumably, shipping is still free.