As posted one of the new southwest app updates is a bag sizing tool that lets you know if your bag is too big for a carry-on and  you should check it instead    the app works pretty well and definitely suggest it if you have concerns about your bag.  Here’s a screenshot from the app  Measured well  First  you move your camera towards the floor so it can detect it -then it gives you the option to press start -and these green dots will pop up. I suggest moving your camera around the bag so more of these connecting dots pop up and it can accurately detect the bag volume   the more dots the better but it’s important the camera can see all sides  of the bag           It works prettty well but can definitely be tricky so here are some things I found worked    -tuck all straps if measuring a backpack -use a well-lit space so the app can detect volume, for this reason also avoid colors that blend together - you can Use it on a table or floor as long as it’s a flat surface but make sure there’s no other items in camera view that can get in the way  -you can walk away with your phone  and come back to the space and the measurement box will stay in the same spot  once it’s scanned so you can get your friend to show them that the bag definitely can/can’t be checked in      Here’s an example of straps out, two walls and competing volumes. The dots were all over the place !        With straps out and against a white wall it’s hard to detect the bag dimensions   Overall great feature and better than other similar tools!              ... View more