A fitted sheet starts with a flat rectangle and elastic in the corners
A crib fitted sheet is a flat piece of fabric with elastic sewn into the four corners so it pulls tight and stays on the mattress. You start with a rectangle of fabric cut to the crib mattress size plus seam allowance, sew a pocket at each corner, insert elastic through those pockets, and stitch the elastic closed. The whole project takes two to three hours if you have a sewing machine and basic skills.
The key difference from a regular sheet is the corner construction. Instead of folding fabric like a fitted sheet for a bed, you cut away a square from each corner, fold the raw edges inward, and create a channel for elastic. When you pull the elastic tight and find it, the corners cup under the mattress.
Key Takeaways
- Measure your crib mattress and add half an inch on all sides for seam allowance before cutting your fabric.
- Cut a square from each corner (usually 2 to 3 inches), then fold and sew the raw edges to create an elastic channel.
- Use quarter-inch elastic or fold-over elastic rated for stretch; standard elastic will lose its grip after washing.
- Test the fit on your mattress before sewing the elastic ends closed, because too-tight elastic will tear the fabric and too-loose elastic will slip off.
Measure your crib mattress and add seam allowance
Standard crib mattresses are 28 inches wide by 52 inches long. Measure your own mattress to confirm, because some portable or play-yard mattresses are smaller. Write down the width and length.
Add half an inch to the width and half an inch to the length. This is your seam allowance. If your mattress is 28 by 52, your fabric rectangle should be 29 by 53 inches. Cut your fabric to this size using a rotary cutter and ruler, or mark the lines with chalk and cut with scissors.
Cut corner squares and fold the edges
At each corner of your rectangle, mark a square. The square should be 2 to 3 inches on each side — the exact size depends on how thick your mattress is. A standard crib mattress is about 5 inches thick, so 2.5-inch squares work well. Cut out all four corner squares with scissors or a rotary cutter.
Now you have a cross shape. Fold the raw edge of each arm inward by half an inch and press with an iron. Fold it inward again by half an inch and press. This double fold hides the raw edge and creates a finished edge. Pin the fold in place.
Sew along the folded edge with a straight stitch, using a thread color that matches your fabric. Sew all four sides of the cross. This stitching holds the fold in place and creates a channel that will hold the elastic.
Insert elastic through the corner channels
Cut four pieces of elastic, each about 8 to 10 inches long. Use quarter-inch-wide elastic or fold-over elastic designed for sewing — do not use hair elastic or craft elastic, which will not hold up to washing. Attach a safety pin to one end of the first elastic piece.
Starting at one corner, feed the safety pin through the channel you just created. Push it all the way around the corner and out the other side. The elastic now runs through the folded edge at that corner. Repeat for all four corners.
Before you sew the elastic closed, try the sheet on your mattress. Pull the elastic tight so the corner cups under the mattress edge, and hold it there. The sheet should fit snugly without puckering. If it is too tight, the fabric will tear; if it is too loose, the sheet will slip. Adjust the elastic length until the fit is right.
Sew the elastic ends closed and finish the edges
Once the fit is correct, overlap the two ends of the elastic at each corner by about half an inch. Sew back and forth over the overlap several times with a zigzag stitch to find it. The zigzag stitch stretches with the elastic and will not snap when you wash the sheet. Trim any excess elastic.
Fold the raw edges of the main sheet body inward by half an inch and press. Fold again by half an inch and press. Sew this hem with a straight stitch all the way around. This finishes the edges and prevents fraying.
Wash the sheet in warm water with mild detergent and dry on low heat. The elastic will relax slightly after the first wash, which is normal. If the fit is still good after washing, you are done.
Fabric and elastic choices that last
Use 100 percent cotton quilting fabric or cotton sateen for durability. These fabrics hold up to frequent washing and do not pill. Avoid thin cotton blends or jersey knit, which wear out faster and may sag around the corners.
For elastic, buy fold-over elastic or quarter-inch braided elastic from a fabric store, not a craft store. Fold-over elastic is wider and easier to sew; braided elastic is thinner and less visible. Both are rated for stretch and recovery, meaning they will not lose their grip after 20 or 30 washes. Standard elastic will flatten and stop holding the sheet in place.
Thread color matters less than thread quality. Use all-purpose polyester thread in a color that blends with your fabric, or use white or cream if your fabric is light. Cheap thread breaks easily and leaves gaps in your seams.
Common mistakes and how to avoid them
The most common mistake is cutting corner squares that are too small. If the squares are smaller than the mattress thickness, the folded edges will not reach around the corner, and the elastic channel will be incomplete. Measure your mattress thickness and add a quarter inch to be safe.
The second mistake is using the wrong elastic. Hair elastic, craft elastic, and cheap elastic lose their stretch after a few washes. The sheet will slip off the mattress. Spend the extra dollar or two on sewing-grade elastic.
The third mistake is sewing the elastic ends with a straight stitch instead of a zigzag. Straight stitches do not stretch, so they snap when the elastic relaxes. Always use a zigzag stitch for elastic.
The fourth mistake is not testing the fit before sewing the elastic closed. If the elastic is too tight, you will have to cut it open, adjust it, and sew it again. Test first, sew second.
Frequently Asked Questions
Can I use a serger instead of a regular sewing machine?
Yes. A serger finishes the raw edges as it sews, which is faster and looks more professional. Use a three-thread or four-thread serger stitch for the hems and a zigzag stitch for the elastic ends. If you do not have a serger, a regular machine with a zigzag stitch works just as well.
What if my crib mattress is not standard size?
Measure your mattress width and length, add half an inch to each, and cut your fabric to that size. The corner square size stays the same — 2 to 3 inches — because it depends on mattress thickness, not mattress size. Portable crib mattresses are usually 38 by 24 inches; measure yours to be sure.
Can I make a fitted sheet without a sewing machine?
You can hand-sew it, but it will take six to eight hours and the seams will be weaker. If you hand-sew, use a backstitch for all seams and make your stitches as small and close together as possible. A sewing machine is worth borrowing or renting for this project.
How much fabric do I need to buy?
Buy one yard of 44-inch-wide fabric. One yard is 36 inches long, which is enough for a standard crib sheet with a little left over. If your crib is larger than standard, measure the length you need and add 2 inches for safety.
Do I need to pre-wash the fabric?
Yes. Wash and dry the fabric before you cut it, using the same water temperature and dryer setting you will use for the finished sheet. Fabric shrinks, and pre-washing prevents the sheet from shrinking after you sew it and make it unwearable.