A fitted sheet is a flat sheet with elastic sewn into the corners
A fitted sheet starts as a rectangle of fabric. You cut it to size, fold the corners into triangles, sew a casing (a tube of fabric) around the inside of those corners, and thread elastic through the casing. When you pull the elastic tight, the corners cup up and grip the mattress. The flat sides stay flat, and the elastic holds everything in place.
The process takes about two to three hours if you have a sewing machine and have done it before. If this is your first time, budget four to five hours. You will need a sewing machine, thread, elastic, fabric scissors, a measuring tape, pins, and a needle for hand-sewing the final seam. Most of the work is straightforward; the corners are where precision matters.
The hardest part is not the sewing—it is the math. You need to know your mattress depth (how thick it is) and your sheet size (twin, full, queen, king). Those two numbers determine how much elastic you need and where to cut your corners. Get those right, and the rest follows a straightforward pattern.
Key Takeaways
- A fitted sheet is a flat rectangle with elastic-filled casings sewn into the four corners so they cup up and grip the mattress.
- You need to measure your mattress depth and know your sheet size before you cut, because the corner size depends on both numbers.
- The corners are made by folding the fabric into triangles, sewing a casing around the inside edge, and threading elastic through the casing.
- A sewing machine makes the work much faster, but you can hand-sew a fitted sheet if you have the time and patience.
- The final seam where the two ends of the casing meet is usually hand-sewn to keep it neat and hidden inside the fold.
Measure your mattress and choose your fabric size
Start by measuring three things: the width of your mattress, the length of your mattress, and the depth (thickness). Write these down. A standard queen mattress is 60 inches wide, 80 inches long, and usually 9 to 12 inches deep, but yours may differ.
Your fabric rectangle needs to be larger than the mattress top by twice the depth, plus 15 inches for the seam allowance and elastic casing. For a queen mattress that is 9 inches deep, the formula is: width = 60 + (2 × 9) + 15 = 93 inches; length = 80 + (2 × 9) + 15 = 113 inches. If your mattress is 12 inches deep, add 24 instead of 18, which gives you 99 × 119 inches.
Buy fabric that is at least 1 to 2 inches larger in each direction than your calculation, because you will trim it square and even before you start. Quilting cotton, jersey knit, and flannel all work well. Avoid stretchy fabrics unless you have sewn with them before—they are harder to control.
Cut the corners into squares and mark the fold lines
Lay your fabric flat on a large surface. Measure from one corner along both edges a distance equal to your mattress depth plus 7 inches. For a 9-inch-deep mattress, that is 16 inches. Mark that point on both edges with a pin or chalk. Do this at all four corners.
Draw a line connecting the two marks at each corner, creating a square. The side of each square equals your mattress depth plus 7 inches. Cut along these lines and remove the four corner squares. You now have a cross-shaped piece of fabric with four rectangular flaps hanging from each side.
Fold each flap up so the two cut edges meet. Press the fold with an iron or your hand. This fold line is where your elastic casing will go. Pin along the fold to hold it in place while you sew.
Sew the casing and thread the elastic
Set your sewing machine to a straight stitch. Sew along the fold line you just made, starting at one corner flap and going all the way around. Sew about 1 inch from the fold—this creates a tube (the casing) between the fold and your seam line. Leave a 2-inch gap on one side so you can thread the elastic through later.
Measure the perimeter of your mattress top (width + length + width + length). For a queen, that is 60 + 80 + 60 + 80 = 280 inches. Cut a piece of elastic that is about 10 to 15 inches shorter than this number. For a queen, cut elastic that is 265 to 270 inches long. Thinner elastic (0.5 inches wide) is easier to thread; thicker elastic (1 inch) is more durable.
Attach a safety pin to one end of the elastic and feed it through the casing opening. Work it all the way around the sheet, pushing the fabric along the elastic as you go. When the elastic comes out the other end, overlap the two ends by 1 inch and sew them together with a needle and thread or a quick machine stitch. Tuck the joined elastic back into the casing and hand-sew the opening closed with a ladder stitch or whip stitch.
Sew the side seams and finish the edges
Fold the sheet in half with the right sides facing each other (the pretty side of the fabric touching). The elastic-filled corners should be on the inside. Pin the two long sides together where the corner flaps meet.
Sew a straight seam along both sides, using a 0.5-inch seam allowance. Start at the corner and sew toward the center, stopping about 6 inches before the middle. Do the same from the other end. This leaves a gap in the middle of each side seam—that gap is where the elastic corners will sit when the sheet is turned right-side out.
Trim the seam allowance to 0.25 inches and finish the raw edges with a zigzag stitch or pinking shears to prevent fraying. Turn the sheet right-side out through one of the gaps. Push the corners out so they are fully formed. Hand-sew the gaps closed with a ladder stitch.
Press and test the fit
Iron the entire sheet on a low to medium heat setting, paying special attention to the corners and edges. The elastic should pull the corners into a cup shape that is even on all sides. If one corner is tighter or looser than the others, the elastic may not be threaded evenly—you can carefully open that corner, adjust the elastic, and sew it closed again.
Put the sheet on your mattress and check the fit. The corners should grip firmly without bunching, and the flat sides should lie smooth. If the sheet is too loose, the elastic was cut too long; if it is too tight, the elastic was cut too short. For your next sheet, adjust the elastic length by 5 to 10 inches in the direction you need.
Wash the sheet in warm water and dry it on low heat. The elastic will relax slightly after the first wash, which is normal. If the sheet still does not fit after washing, you can open one corner, remove the elastic, cut a new piece, and re-thread it.
Hand-sewing instead of machine sewing
If you do not have a sewing machine, you can sew a fitted sheet by hand using a needle and thread. Use a backstitch for all seams—it is the strongest hand stitch and creates a seam that looks similar to a machine stitch. Work in good light and take small, even stitches (about 0.25 inches long).
Hand-sewing the casing takes the longest. Sew slowly and do not rush. The side seams and corner closures go faster because you are sewing through only two layers of fabric instead of the folded casing. A hand-sewn fitted sheet will take six to eight hours, but the result is just as durable as a machine-sewn one if your stitches are tight and even.
Frequently Asked Questions
What size elastic should I use?
Use elastic that is 0.5 to 1 inch wide. Narrower elastic (0.5 inches) is easier to thread through the casing and works well for most sheets. Wider elastic (1 inch) is thicker and more durable but harder to feed through a narrow casing. Avoid elastic narrower than 0.5 inches—it will roll and twist inside the casing.
Can I use a different fabric for the casing?
Yes. Some people use a contrasting fabric for the casing so the elastic is easier to see and thread. Cut a strip of fabric 3 to 4 inches wide and long enough to go around the perimeter of your sheet. Sew it to the inside of the corner fold instead of folding the sheet fabric itself. This adds a step but makes threading the elastic simpler.
What if my corners are bunching or not staying tucked?
Bunching usually means the elastic is too tight or the corner is too small. Loose corners mean the elastic is too long or the corner is too large. Open the corner, measure the elastic length, and adjust it by 5 to 10 inches. You can also make the corner square larger or smaller by re-cutting and re-sewing.
How do I know if my seam allowance is right?
A standard seam allowance for fitted sheets is 0.5 inches. If your sheet is too small, use a smaller seam allowance (0.25 inches) next time. If it is too large, use a larger seam allowance (0.75 inches). Keep notes on what worked so you can repeat it for your next sheet.
Can I sew a fitted sheet with a serger?
Yes. A serger finishes the raw edges as it sews, which saves a step. Use the same seam allowance and follow the same pattern. The serger will trim and bind the edges in one pass, making the sheet more durable and less likely to fray.