How deep is 'deep pocket' versus 'extra deep pocket'?

Most brands label 13–15" as standard pocket, 16–17" as deep pocket, and 18"+ as extra deep. If your mattress alone is 12–14" and you use a topper, plan on at least 18". For mattresses 20" and over (common with pillow-top hybrids and adjustable bases), look for sets explicitly rated 18–24" like the Hearth & Harbor and CGK Unlimited sets on this list.