Its supposed to be 8 and it definitely didnt get up to 8 maybe 4 to 4 and a half in some spots.. not worth the buy!! It said to let sit for 72 hours so i did 4 days just incase an it still sucks! My bed doesnt require a box spring so you could feel the metal under the mattress its so thin. Plus its loud!!! It makes a noise everytime you move. Dont waste your time or money!