All airlines place limits on the number, the size, and the weight of what you can carry on to a flight with you. Generally US domestic airlines are fairly liberal with these limits, and rarely choose to enforce them.

When maximum size measurements are shown as a total number of inches (eg 45″) this is the total of the length, width and height of the piece. There are standard sets of dimensions that go to make up these totals (for example, 22 x 14 x 9 is the standard for 45″) and if you have a bag that is an unusual shape but still within the total number of inches, you may find it being rejected.

Click here more on all airline carry-on restrictions.