The US Army is a disciplined institution. Wearing the prescribed uniform and having a good personal appearance is part of the discipline each member of the service demonstrates to show his or her pride in being part of an effective military force. The US Army uniform is to be worn whenever personnel are on duty. For complete details about the US Army uniform regulations, you can download a pdf of AR 670-1.
All personnel will maintain a high standard of dress and appearance. This means that you must ensure that your uniform fits correctly; not tightly or loose. Uniforms are to be kept clean and dress uniforms should be pressed when necessary. Lapels and sleeves of service, dress, and mess coats and jackets will be roll-pressed, without creasing. Skirts should not be creased. Slacks and the sleeves of shirts and blouses will be creased.
Headgear is to be worn whenever the uniform is worn, except when: 1) it interferes with the safe operation of military vehicles, 2) soldiers are indoors, or 3) may chose not to wear headgear when attending evening social events (after Retreat) when wearing a dress or mess uniform. Headgear is to be carried by hand when not worn. Soldiers are authorized to store headgear in the BDU cargo pockets as long as the headgear is folded neatly. Soldiers are not to attach headgear to the uniform or hang it from the belt.
Soldiers may wear a wristwatch, a wrist identification bracelet, and a total of two rings when in uniform. Any jewelry worn must be conservative and in good taste. Only one item may be worn on each wrist. Other than the above jewelry (and some religious exceptions), no other jewelry shall be exposed while wearing the uniform other than a conservative tie tack or tie clasp with the four-in-hand necktie.
Male personnel may not attach, affix, or display objects, articles, jewelry, or ornamentation to or through the skin while in uniform, in civilian clothes on duty, or in civilian clothes while off duty. This goes for ALL skin and not just exposed skin, so the above applies to one's tongue, lips, inside of mouth, nipples, navel, and other covered body parts.
Females are permitted to wear earrings that conform to the following standards while in uniform. Earrings must be screw-on, clip-on, or post-type earrings in gold, silver, white pearl, or diamond. They must be a quarter of an inch or smaller, unadorned, spherical, and fit snugly against the ear. Earrings can only be worn as a matching pair and only one earring per earlobe. Earrings are not permitted with any class C uniform (such as BDU, hospital duty, food service, physical fitness).
Conservative civilian prescription eyeglasses are authorized for wear with all uniforms. Prescription and nonprescription sunglasses (with a conservative appearance) are authorized when in a garrison environment, except when in formation and while indoors. Eyeglasses or sunglasses that have decorations on the frame or lenses are not permitted. Only shades of gray, brown, and dark green are allowed for sunglasses' lenses. Personnel can not use chains, bands, or ribbons on eyewear and are not allowed to hang glasses (or eyeglass cases) on the uniform.