A coaster is two pieces of fabric sewn together with a folded edge

A coaster is the easiest sewing project for a beginner because it has only four straight seams and no curves. You cut two squares of fabric, place them face-to-face, sew three sides closed, turn it right-side out through the fourth side, and then sew that fourth side shut. The whole project takes about an hour once you have your materials, and you end up with something you can actually use.

You do not need a sewing machine—hand sewing works just as well and teaches you better control. A machine is faster, but a needle and thread will get you the same result. The key is using a seam allowance (the space between the edge of the fabric and your stitching line) of about half an inch on all sides, because that gives you room to work and keeps the seam from unraveling.

Key Takeaways

  • Cut two identical squares of fabric, each about 5 inches by 5 inches, which leaves room for a half-inch seam allowance on all sides.
  • Place the two squares face-to-face (right sides together), pin three sides, and sew along those three sides with a half-inch seam allowance.
  • Turn the coaster right-side out through the unsewn fourth side, push the corners out with a blunt tool, and press flat with an iron.
  • Fold the raw edges of the fourth side inward by half an inch, pin them closed, and sew them shut with a ladder stitch or running stitch.
  • A coaster finished this way will last through years of use because the seams are enclosed and protected inside.

Gather your materials before you start

You need two pieces of fabric, each at least 5 inches by 5 inches. Cotton quilting fabric or cotton from an old shirt works well. Avoid stretchy fabrics like knits or jersey—they slip around and make straight seams harder. If you want a coaster that absorbs water, use two layers of regular cotton. If you want it waterproof, use one layer of cotton and one layer of cotton-backed vinyl or oilcloth.

You also need a needle (size 70/10 or 80/12 for cotton), thread that matches your fabric or contrasts intentionally, scissors that cut fabric cleanly, pins, and an iron. If you are hand sewing, a thimble protects your finger from the needle. If you are using a machine, thread it before you start and test it on scrap fabric first.

Cut your fabric squares and mark your seam line

Cut two squares that are exactly the same size. A 5-inch square is a good size for a coaster—large enough to hold a mug, small enough to finish quickly. Use a ruler and a pencil or fabric marker to draw a light line on the wrong side (the back) of one square, half an inch in from each edge. This is your seam line, and it keeps your stitches straight and even.

You do not have to mark every side if you are confident, but marking one or two sides helps you stay on track, especially on your first coaster. The seam line is where your needle goes; the half inch beyond it is where you trim later.

Pin and sew three sides with right sides together

Place the two fabric squares face-to-face so the marked side faces outward. This is called right sides together. Pin along three of the four sides, placing pins every inch or so perpendicular to the edge. Leave one full side unpinned—this is your opening for turning the coaster right-side out later.

If you are hand sewing, thread your needle, tie a knot at the end, and start at one corner of a pinned side. Push the needle through both layers from the back, and bring it up half an inch along the seam line. Make small, even stitches (about an eighth of an inch long) along the marked line. At each corner, sew right to the corner point, then pivot and sew along the next side. When you reach the end of the third side, tie off your thread on the back.

If you are using a machine, set the stitch length to 2.0 or 2.5 (medium length), place the fabric under the presser foot with the marked line aligned under the needle, and sew slowly along all three pinned sides. Backstitch at the start and end of each side to lock the stitches. Trim the corners diagonally, cutting close to the stitching but not into it—this reduces bulk when you turn the coaster right-side out.

Turn the coaster right-side out and press it flat

Reach through the unsewn opening and gently pull one corner of the coaster toward you. Keep pulling until the whole thing turns inside out and the right sides (the pretty sides) are now facing outward. This takes a little patience on your first try, but it works every time.

Use a blunt tool—the eraser end of a pencil, a chopstick, or a point turner—to push each corner out from the inside so the corners are sharp and square, not rounded. Then lay the coaster flat on an ironing board and press it with a warm iron (no steam). Pay special attention to the edges so they lie flat. This makes the final seam much easier to sew and makes the coaster look finished.

Fold, pin, and sew the fourth side closed

Fold the raw edges of the unsewn opening inward by half an inch on both sides, and press them with the iron so they stay folded. Pin the opening closed, placing pins perpendicular to the fold. Now you sew this opening shut, and you have two choices: a ladder stitch (also called a slip stitch), which is nearly invisible, or a running stitch, which is visible but faster.

For a ladder stitch, thread your needle and bring it up through the fold on one side of the opening. Slide the needle along inside the fold for about half an inch, then push it straight across through the fold on the opposite side. Slide the needle inside that fold for half an inch, then come back across. Keep going back and forth, and every few stitches, gently pull the thread to close the opening. The thread runs inside the fold and barely shows on the outside. When you reach the end, tie off inside the fold.

For a running stitch, straightforward sew along the opening the same way you sewed the other three sides, using the same half-inch seam allowance. This stitch is visible on the outside, so it works best if you want a decorative line or if your thread matches your fabric.

Trim loose threads and test your coaster

Once the fourth side is sewn, trim any loose thread ends close to the fabric. Press the coaster one more time with the iron, paying attention to all four edges. The coaster should be flat, square, and firm enough to hold a mug without bending.

Set a wet mug on it to test. If water soaks through, your coaster is working as a regular cotton coaster—it will absorb moisture and dry out. If you used oilcloth or vinyl on one side, water should bead up and stay on top. Either way, your coaster is done and ready to use or give as a gift.

Frequently Asked Questions

Can I use a sewing machine if I have never used one before?

Yes, but practice on scrap fabric first. Thread the machine, set the stitch length to medium (2.0 to 2.5), and sew a few straight lines on fabric scraps to get a feel for how fast the needle moves and how to guide the fabric. Once you are comfortable, sewing a coaster on a machine takes about 15 minutes.

What if my corners are not square when I turn it right-side out?

Use a point turner or the eraser end of a pencil to push each corner out from the inside. Work gently so you do not poke a hole in the fabric. Then press the coaster with an iron, which flattens the corners and makes them look square.

Should I use a ladder stitch or a running stitch for the fourth side?

A ladder stitch is nearly invisible and looks more polished, but it takes longer and requires practice. A running stitch is faster and works just as well. If your thread matches your fabric, either stitch looks fine. If you want to hide the seam, use a ladder stitch.

Can I make a coaster without an iron?

Yes, but pressing makes a big difference in how flat and finished the coaster looks. If you do not have an iron, press the coaster under a heavy book overnight instead. It will not be quite as crisp, but it will still work.

What size should my coaster be?

A 5-inch square is standard and holds most mugs. If you want a smaller coaster for tea cups, cut 4-inch squares. If you want a larger one for water glasses, cut 6-inch squares. Just make sure both pieces are the same size.