What You Need to Know Before You Start
A mattress cover is a flat fabric envelope that slides over a mattress to protect it from dust, spills, and wear. You sew it from four fabric panels—two for the top and bottom, two for the sides—then join them with a seam that runs around the perimeter. The opening stays unsealed so you can slip the cover on and off. Most home sewers complete one in three to five hours, depending on mattress size and sewing speed.
The key difference from other sewing projects is that you are working with a large, bulky piece once the panels are joined. This means your sewing machine needs to handle thick fabric (usually quilting cotton or canvas), and you need a workspace big enough to maneuver the cover as you sew. A standard twin mattress cover uses about 6 to 8 yards of fabric; a queen uses 8 to 10 yards.
Key Takeaways
- Measure your mattress length, width, and thickness, then add seam allowance and ease to each dimension before cutting fabric panels.
- Sew the four panels together using a straight stitch with a 1/2-inch seam allowance, leaving one long side completely open for turning and sliding the cover onto the mattress.
- Press seams flat with an iron after each seam to keep the cover square and prevent puckering when you put it on the mattress.
- Use a needle size 80/12 or 90/14 and thread rated for quilting or general sewing to avoid breakage on thick fabric.
Measuring Your Mattress and Calculating Fabric Dimensions
Lay your mattress on a flat surface and measure three things: the length (head to foot), the width (side to side), and the thickness (top to bottom). Write these numbers down. A standard twin mattress is 39 inches wide by 75 inches long by 8 inches thick, but your mattress may vary.
Add 1 inch to the length and width for seam allowance (1/2 inch on each side). Add 2 inches to the thickness to account for the fabric wrapping around the edge and sitting flat on top. So a twin mattress would need panels cut to 40 inches wide by 76 inches long, with side panels 10 inches tall (8 inches plus 2 inches).
You will cut four panels: one for the top, one for the bottom, and two for the sides. The top and bottom panels are the full length and width (40 by 76 inches in the twin example). The side panels run the full length (76 inches) and are as tall as your thickness plus 2 inches (10 inches). Write down all four dimensions before you buy fabric.
Choosing Fabric and Preparing Your Panels
Use a medium-weight woven fabric like quilting cotton, canvas, or linen. These fabrics are sturdy enough to protect a mattress and straightforward to sew on a home machine. Avoid stretchy knits or very thin fabrics—they will sag and tear under the weight of the mattress. Check the bolt width before you buy; most quilting cotton is 44 to 45 inches wide, which affects how much yardage you need.
Wash and dry your fabric before cutting if you plan to wash the finished cover. This prevents shrinkage later. Press all panels with an iron set to the heat level recommended on the fabric bolt. Lay your fabric on a large, flat surface—a design table, clean floor, or two tables pushed together work well. Use a rotary cutter and ruler, or a measuring tape and fabric scissors, to cut your four panels to the dimensions you calculated.
Stack the cut panels in order: top, bottom, side one, side two. Check that all edges are straight and all corners are square by measuring diagonally from corner to corner—both diagonals should be the same length.
Sewing the Four Panels Together
Thread your machine with thread rated for quilting or general sewing. Insert a size 80/12 or 90/14 needle, which is sturdy enough for multiple fabric layers. Set your machine to a straight stitch with a stitch length of 2.5 to 3.0 millimeters. Test the tension on a scrap of your fabric folded twice; the thread should not bunch on either side.
Place the top panel and one side panel with right sides together (the pretty sides facing each other). Align one long edge of the side panel with one long edge of the top panel. Pin every 6 inches along the seam. Sew with a 1/2-inch seam allowance, removing pins as you approach them. Backstitch at the start and end of the seam. Press the seam flat with an iron, pressing the seam allowance toward the side panel.
Repeat this step to attach the second side panel to the opposite long edge of the top panel. You now have a U-shape: the top panel with two side panels hanging down on either side. Attach the bottom panel to the free long edges of both side panels the same way, sewing one side at a time and pressing after each seam. You will have a complete box with one long side still open.
Do not sew the opening closed. This is where you will turn the cover right-side-out and slide it onto the mattress. Trim any loose threads and press all seams one final time.
Turning the Cover Right-Side-Out and Fitting It
Reach through the open side and grab the top panel from the inside. Pull it through the opening, turning the entire cover inside-out as you go. This takes patience with a large cover—work slowly and smooth out wrinkles as you pull. Once the top is through, the cover will be right-side-out with the seams hidden on the inside.
Press the entire cover with an iron, paying special attention to the seams and corners. Use a pressing cloth (a thin cotton cloth or pressing sheet) between the iron and your fabric to avoid shine marks. Press the edges of the open side flat as if they were sewn, creasing the fold line sharply.
Slide the cover onto your mattress by centering the mattress inside the open side and pulling the fabric up and around it. Smooth out wrinkles and make sure the cover sits evenly on all sides. The open edges will overlap slightly on the underside of the mattress—this is normal and helps keep the cover in place.
Common Mistakes and How to Avoid Them
The most common error is cutting panels that are too small. Mattresses vary in thickness, and even 1 inch of missing fabric will make the cover too tight to slide on. Always measure your specific mattress and add the full 2 inches to the thickness dimension. If your cover is too tight after you finish, you cannot easily fix it—you would need to unsew one seam and add a fabric strip.
Another frequent problem is uneven seams that cause the cover to sit crooked on the mattress. Prevent this by pinning every 6 inches before you sew, and by pressing each seam flat when ready after sewing it. Wrinkled seams are harder to align with the next panel, and they create puckers that throw off the whole shape.
Some sewers sew the opening closed by mistake, then have to unsew it to turn the cover right-side-out. Mark the opening side with a safety pin or piece of tape before you start sewing, and double-check your seam plan on paper before you begin.
Finishing Touches and Care
Once the cover is on the mattress, you can add a straightforward topstitch along the open edges if you want them to look more finished. This is optional—the overlapped edges on the underside hold the cover in place without stitching. If you choose to topstitch, use a thread color that matches your fabric and sew 1/4 inch from the folded edge, backstitching at the start and end.
Wash your mattress cover in cool water on a gentle cycle, and dry it on low heat or hang it to air dry. Do not bleach it unless the fabric bolt says bleach is safe. Remove the cover from the mattress before washing to avoid putting stress on the seams. A well-made cover will last through many washings if you treat the seams gently.
Frequently Asked Questions
Can I use a serger instead of a regular sewing machine?
Yes. A serger creates a more finished seam and trims the fabric edges as it sews, which looks professional. Use a 4-thread serger stitch for strength. You still need to leave one side open for turning and fitting the cover onto the mattress.
What if my mattress is thicker than 8 inches?
Measure your actual mattress thickness and add 2 inches to that number for the side panel height. A pillow-top or memory foam mattress may be 12 to 14 inches thick—measure it before you cut fabric.
Do I need to add elastic or ties to keep the cover from sliding?
No. The overlap on the underside of the mattress holds the cover in place through friction. If your cover slides during use, the mattress may be thinner than you measured, or the fabric may be too slippery. Quilting cotton and canvas usually grip well enough without elastic.
Can I sew a mattress cover by hand?
You can, but it will take 15 to 20 hours for a queen-size cover because you are sewing through multiple layers of thick fabric. A machine stitch is much faster and stronger. If you do hand-sew, use a backstitch and thread rated for heavy fabric.
What size needle and thread do I use for thick fabric?
Use a size 80/12 or 90/14 needle with thread rated for quilting or general sewing. Thinner needles (size 60/8 or 70/10) will bend or break on multiple layers. Lightweight thread may snap under tension.