FAQ MATTRESSES HOW TALL IS THE CASPER MATTRESS? SEE ALL QUESTIONS HOW TALL IS THE CASPER MATTRESS? The Casper mattress is 10 inches thick. This means the Casper mattress is suited to all standard size sheets — but we always recommend using Casper Sheets! YOU MAY ALSO LIKE What are the dimensions of the Casper mattress? Once I take my mattress out of the box, how long does it take to expand? Can I use an adjustable base or Murphy bed? Will my sheets fit on a Casper? What’s the difference between a bunkie board and a box spring?