Alazzo Clothing demonstrates how to measure pant length. Measuring pant length is important when ordering clothing online or ordering custom made clothing to ensure a good fit. To measure the length of pants, place a tape measure at the top of the pants waist. Hold the tape securely and then bring it down to the bottom of the pants. You can also measure to one inch from the ground. When measuring pants length, be sure to follow the seam. Utilizing the pants waist to bottom of the pants method will give you an accurate reading as to the length of the pants.