Product gets to 3" thick only because of the egg crate peaks. I didn't expect the peaks/valleys to be so extreme -- I'd say the thinnest part of the mattress is a bit less than an inch. Having said that, the mattress topper does not disappoint. Perfect addition to a firm bed. Expected topper to hold too much body heat and make for uncomfortably hot sleeping -- so far, this has NOT been a problem. Will probably order more, but may try another type for comparison.