Many people prefer to make their beds with fitted sheets rather conventional flat sheets because it saves time. If you have a sewing machine and some extra flat sheets, it’s relatively easy and quick to custom sew fitted sheets from your flat sheets instead of buying new ones.
Measure the length, width and depth (or thickness) of the mattress using a cloth measuring tape. Add an additional 6 to 8 inches to each measurement for tucking. If your flat sheet is not wide enough, you can allow fewer inches to tuck under the mattress. You just need to make sure that when you are finished sewing the fitted sheet, the amount of sheet to be tucked under is the same around all sides of the mattress.
Remove the hem from the flat sheet with a seam ripper. Be careful as you cut the threads of the hem so that you do not pull the fabric. Later you will turn under the edges of the sheet to stitch a new hem.
Lay the sheet right side down on top of the mattress. Smooth the sheet evenly over the mattress.
Pull the sheet in to fit at each corner and then pin a dart. Darts should measure the height of the mattress plus the number of inches you are allowing for tucking the sheet under.
Trim off the extra fabric with sharp fabric shears, and then sew the dart using a zigzag stitch. You should have a seam allowance of about ½ inch. Still working on the wrong side, turn up the edges of the sheet ¼ inch, and then fold up ¼ inch again. After pressing the hem in place, sew it evenly along the edge of the sheet.
Cut four pieces of either ¼- or ½-inch-wide elastic, each 10 inches in length. Beginning at one corner, center a piece of elastic at the bottom of the dart. Make sure that you are working on the wrong side of the sheet before stretching the elastic along the bottom edge of the sheet.
Attach the elastic to the corner using a zigzag stitch, while at the same time keeping the elastic stretched as you work. Sew elastic onto the other three corners following the same procedure.
A zigzag stitch looks something like a cross-stitch. Stronger than a straight stitch, a zigzag stitch helps to keep the unfinished edges of a fabric from fraying.