Dorm Size Bed Dimensions are generally 39 inches wide x 80 inches long. These are standard Dorm bed measurements. Dorm Mattress depths can vary from just a few inches to 7" or more. Many times, actual dorm mattress dimensions will vary by one or two inches, usually smaller. Dorm mattresses are often covered with a vinyl medical grade covering so they can be cleaned and disinfected. Sometimes these coverings have tears and micro abrasions that can harbor a very nasty group of disease organisms. Further, these vinyl coverings do not breathe and so can be very uncomfortable to sleep on. I highly suggest that a fully enclosed mattress covering like the ones we sell be used on your dorm bed plus a nice quilted mattress pad.