Thank you for purchasing one of our mattresses. This is a great question. The first rule of thumb is if your mattress has reached its full height and size, it should be ready to use. But expansion times may vary depending on how long it has been in the packaging. It can take anywhere from 24-48 hours. Because our mattresses are compressed and sealed for shipping convenience, it may take time and a little patience. Hang in there. And if the majority of your mattress has expanded and you’re waiting for the last inch or two, it may help to go ahead and sleep on it. Body heat to the foam is likely to speed up the process.