The Standard Size of a Full Size Box Spring. The dimensions of a full size bed are 75 inches long and 53 inches wide. It features a box spring that is approximately 5 to 5.5 inches high for the low profile version, while the high profile version has a standard height of 9 inches. A box spring has three basic purposes. The first one is to create a firm and flat structure that is perfect enough to put the mattress on top.