To measure a bag at home accurately for 2026 airline standards, you need to measure three dimensions: Height, Width, and Depth. The most critical mistake people make is not including the "protrusions." To get the true height, place the bag upright on a flat floor and measure from the floor to the very top of the carry handle (ensure the telescopic handle is fully pushed in). This must include the wheels. For width, measure across the widest part of the bag, including any side handles or bulging side pockets. For depth, lay the bag flat on its back and measure from the floor to the highest point of the front panel. Airlines look at the "Linear Inches" (Height + Width + Depth), which for most domestic carry-ons must be 45 inches or less. It is highly recommended to measure the bag after it is fully packed, as overstuffing a soft-sided bag can easily add 2 or 3 inches to the depth, which might make it fail the "sizer box" test at the gate. If you have a bathroom scale, you can weigh yourself first, then weigh yourself holding the bag, and subtract the difference to ensure you are under the common 7-10 kg weight limit.