Place the suitcase on a flat surface
Measure the height from the bottom to the top, including wheels and handles if they are fixed
Measure the width across the widest part of the suitcase
Measure the depth from the front to the back at the thickest point
Use a tape measure for accuracy
Record the measurements in inches or centimeters
Check airline size requirements using the total dimensions if needed
Include any external pockets, wheels, and protruding handles if the airline or retailer requires them