The smallest bone in the human body is in your ear and is called the stirrup bone, the stapes, one of the 3 bones that make up your middle ear; measuring 2-3 millimeters (0.10 to 0.13 in) and weighs only 1.98 to 4.3 mg. It shaped like a ‘U’ and is the innermost bone that receives sound vibrations and passes them along to the cochlea to eventually be interpreted by the brain.