[header] How to measure your truck bed [title] Measure your truck bed's length with the tailgate closed. [step] Have a friend help you stretch a tape measure from the front left corner to the back left corner of your truck bed, on the inside. The tape measure should be running in a straight line that's even with the top of the bed (make sure it isn't sagging in the middle). 
Write this measurement down and label it " length. " [title] Find the width of your truck bed.