Sheets are one of those purchases where the size on the front of the pack is the easy part. Whether they stay on the mattress and feel right after a few washes depends on a few other details.
Check the pocket depth
Mattress height has grown over the years. Add the thickness of any topper, then compare it with the stated pocket depth of the sheet.
- Measure the mattress and topper together
- Look for a stated depth, not just "deep pocket"
- Elastic all the way around holds better than corner straps
Fabric and care
Microfibre, cotton and blends all behave differently in the dryer. The care label tells you more than the marketing words do.