Step 1 place your measuring tape at the bulkhead of your truck bed.
How to measure your truck bed for a canopy.
Hold one end of your tape measure against the inside of your truck bed s left front corner and have someone pull the tape measure until it reaches the inside of the front right corner.
Record this measurement and label that number width.
Step 2 moving along your bed rail extend the measuring tape to the inside edge of the top of your tailgate.
Measuring is actually quite easy simply take a tape measure and measure between the bulkhead near the cab inside the truck bed all the way to the inside of the tailgate the pivot point of your tailgate.