Understand how the customary system works by familiarizing yourself with common units of length such as inches, feet, yards and miles. Learn how these units fit together and how many of one unit make up another. For example, 1 mile is made up of 1,760 yards or 5,280 feet, 1 yard is made up of 3 feet or 36 inches, and 1 foot is made up of 12 inches.
Decide on the right tool to use to measure length. Use a foot-long ruler to measure very short things such as a toothbrush, a tape measure to measure your height and a measuring wheel to measure a field.
Position your measuring device so that it stretches between the two points of the object you are measuring. Position the "0" on your measuring device at one point of the object and read the number that meets the second point of the object. The number at the second point of the object is its length.
Express your length using decimals, fractions or combine units. For example, you may travel 10.3 miles (decimal), use a 1 1/4 inch wrench (fraction) or measure 5 foot 10 inches tall (combined units).