How to turn flat sheets into fitted sheets

Fitted bed sheets are one of my favorite modern inventions. It annoys me to my core when flat sheets slip, get crumpled at the corner of the bed and I find myself on the bare mattress in the morning. When I buy a single bed sheet I always opt for fitted ones. However, I also buy duvet covers as a set and most of the bed sheets included in the sets are flat. I used to try to secure them with pins, clips or grippers but it never worked as it should.

I’ve had numerous flat sheets which I haven’t been using for a long time. During a recent phase of purging and decluttering, I’ve decided to donated most of them and turn the 4 flat sheets of the sets I decided to keep into fitted sheets all at one sitting.

I’ve used 2 different methods. For the larger sheets which totally cover the mattresses and can be tucked underneath, I made fully enclosed the corner seams and fitted with elastic bands. For bed sheets that don’t fully cover the mattresses, I just sew large elastic bands at the sides of the corners.

Materials needed:

  • Pins
  • Washable fabric markers
  • Measure tape
  • Scissors
  • Thread
  • Elastic band


Lay the flat bed sheet on the mattress you need to fit for. Center the bed sheet with equal distance from both sides.
IMG_5040 Mark the corner line where you need to sew on the flat bed sheet using pins. Mark where you need to tuck in, i.e. sew the elastic band casing.
Lay flat sheet on a flat surface and mark where you need to cut and sew using washable fabric / sewing marker. Don’t forget to add 5/8” seam allowance on the corner seam.

Once you make sure you’ve properly measured and calculated where the corner seam should go, cut the corners.
You can mark and cut one corner at a time or fold it do two of them at the same time.
Just make sure you’ve centered the bed sheet with even distance from each sides when you are doing the initial measuring.

Pin the corner for the stiching.
Stitch the corner seam and turn it inside out. This corner looks great!
Two sides of the corner might be uneven. Using the shorter side as a guide fold the fabric inside and pin to sew a casing wide enough to house the elastic band. For this type of fitted sheet, I’ve used narrow elastic band.
Sew the fabric inside and fasten the sides of the elastic band on to the edges of the casing. This whole process is not that hard but it takes time to measure properly, pin and sew in the elastic band.
Now repeat this for every corner. You can trim excess fabric at the corners.
As I’ve mentioned, with smaller flat bed sheets, which I couldn’t even tuck in, I wasn’t able to sew a corner seam.
I’ve used large knit elastic band and simply stitched them on the two sides of the corners. I did not sew a casing. The elastic bands stayed exposed.
Here is another example of the exposed elastic band method. I folded the corners and sew them so that the corner wouldn’t extend out and it would look more enclosed.
I stitched the folded ends of the elastic bands behind the fabric using both straight and zigzag stitches so that they keep secured and edges would not tear apart. As expected this method is much easier and quicker to complete.

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