Whether you're keeping track of developing your biceps or simply want to know how big they are, measuring provides the answer. Bodybuilders may measure their biceps before and after a workout to monitor muscle expansion. Others measure the muscles a day after working out to obtain a precise measurement. If you're measuring your bicep for the first time, enlisting the help of a friend or a trainer provides the most accurate result.
Sit at a table and rest your elbow on the tabletop. Double your fist and curl your forearm toward your shoulder. Flex your bicep as hard as possible and hold the flex.
Hold the end of a seamless measuring tape atop the highest point of the bicep. Wrap the measuring tape straight around your upper arm and read the measurement where the tape overlaps the end at the highest point of the bicep to determine the circumference of your upper arm.
Continue to hold your arm curled, open your hand and relax your flex. Take another measurement to determine the expansion of the bicep.
Flex the bicep again. Hold the end of the measuring tape at the base of your bicep on the inside of your arm. Measure over the highest point of the muscle to the base of the muscle at the outside to determine the actual size of the bicep.