Stitching a seam is the most fundamental skill in sewing: you’re joining two pieces of fabric with a line of stitches, typically 5/8 inch from the raw edge on woven fabrics. Whether you’re working by hand or on a machine, the process follows the same basic logic. Pin or clip the fabric pieces together, stitch along a consistent line, then secure and finish the edges. Here’s how to do each part well.
Setting Up Your Fabric
Place your two fabric pieces with their “right” (outer, visible) sides facing each other. The raw edges you’re joining should be aligned evenly. Pin perpendicular to the seam line every few inches to keep the layers from shifting. If you’re working with slippery fabric like silk or satin, pin more frequently or use sewing clips.
Most home sewing patterns use a 5/8-inch seam allowance for woven fabrics. Patterns designed for knits often use 1/4 inch instead. Your pattern will specify, but if you’re working without one, 5/8 inch is the safe default. Mark your seam line with chalk or use the guidelines etched into your machine’s throat plate to keep a consistent distance from the edge.
Choosing the Right Needle and Stitch Length
If you’re sewing on a machine, needle size matters more than most beginners realize. A needle that’s too small for your fabric will bend or break; too large and it leaves visible holes. Use these as starting points:
- Lightweight fabrics (silk, voile, taffeta): size 9/70 needle
- Medium fabrics (cotton, linen, satin): size 11/80 needle
- Medium to heavy fabrics (wool blends, heavier linen): size 14/90 needle
- Heavy fabrics (denim, tweed, canvas): size 16/100 needle
For knits, jersey, and stretch fabrics, switch to a ballpoint needle. Its rounded tip slides between the fabric’s fibers instead of piercing them, which prevents holes and skipped stitches.
Stitch length should also match your fabric weight. Lighter fabrics need shorter stitches (1.8 to 2.5 mm), medium-weight fabrics like cotton poplin do well at 2.0 to 3.0 mm, and heavier materials like denim or canvas need 2.5 to 4.0 mm. Most machines default to around 2.5 mm, which works for general-purpose sewing on medium-weight cloth.
Stitching a Seam by Machine
Line up the raw edge of your pinned fabric with the 5/8-inch guide on your throat plate. Lower the presser foot, then backstitch two or three stitches at the very start. Backstitching locks the thread in place so the seam doesn’t unravel from the end. Then sew forward along the seam line at a steady, moderate speed. Remove pins just before the needle reaches them. When you reach the end, backstitch two or three stitches again before cutting your threads.
One detail that improves results immediately: sew both side seams of a garment in the same direction. On an A-line skirt, for example, stitching one side from hem to waist and the other from waist to hem can make one side longer than the other. This happens because fabric stretches slightly along the bias (any angle that isn’t perfectly parallel to the straight grain). Pick one direction and stay consistent. A good general rule is to stitch with the grain of the fabric. On a tapered pant leg, that typically means sewing from waist to hem. On a flared leg, hem to waist often works better. Run your finger along the fabric’s grain to feel which direction the threads lie smoother, and sew that way.
Stitching a Seam by Hand
When you don’t have a machine or you’re doing a small repair, two hand stitches cover most situations.
The running stitch is the simplest. Push your threaded needle in and out of both fabric layers, taking stitches about 1/4 to 1/2 inch long. You can load several stitches onto the needle at once before pulling the thread through. This stitch works for basting (temporary stitching to hold pieces in place) and for seams that won’t take much stress.
The backstitch is the strongest hand stitch and the one to use for permanent seams. Push the needle up through both layers where you want to start. Bring it back down into the fabric one stitch length behind where the thread came up, then bring it up again one stitch length ahead. Each new stitch goes backward into the hole of the previous stitch, creating a continuous, overlapping line that looks almost like machine stitching on the top side. Keep stitches small and even for the best hold.
To secure the end of any hand-sewn seam, use a lock stitch: push the needle through the fabric, loop the thread back through the previous stitch, and pull tight to create a small knot. Repeat once or twice. This locks the thread at that specific point, preventing the whole seam from loosening.
Pressing Your Seam
Pressing isn’t optional. An unpressed seam looks lumpy and throws off the shape of everything you attach to it next. The question is whether to press the seam allowances open (each flap folded to opposite sides) or press them both to one side.
Press seams open when you want the flattest possible result, especially where multiple seams meet at one point. Bulk stacks up fast at intersections, and opening the seam allowances distributes that thickness. Open seams also make it easier to sew across them later, whether you’re topstitching or quilting over the join. For garment sewing, pressing open is the standard approach for most seams.
Pressing to one side is more common in quilting, where it offers two advantages. First, if one fabric is darker, pressing toward the dark side keeps the seam allowance from shadowing through lighter fabric. Second, when two seams meet, you can “nest” them (one pressed left, the other pressed right) so they lock together for a perfectly aligned intersection. Pressing to one side also shields the thread slightly, because the folded fabric lip sits over the stitching and protects it from abrasion.
Finishing Raw Edges
On most woven fabrics, the raw edges inside your seam will fray over time, especially after washing. You don’t need a serger to deal with this. Four methods work on a standard sewing machine or with basic tools.
Pinking shears are the fastest option. Just trim the raw edges with the zigzag-shaped blades after pressing your seam. Pinking works best on tightly woven fabrics that won’t be washed heavily. It’s less effective on loose weaves like linen.
Zigzag stitch is the most common machine finish. Set your machine to a zigzag (around 1.5 mm length, 3.5 mm width is a good starting point) and sew along each raw edge. You can do this after sewing the seam or before you even join the pieces.
Turn and stitch gives the cleanest look. After sewing your seam, fold each raw edge under by about 1/8 inch, press, and stitch the fold down with a straight stitch. It uses less thread than zigzag methods and produces a neat, flat finish.
Overcast stitch is a built-in option on most machines. It wraps thread around the raw edge in one pass, and some versions let you sew the seam and finish the edge simultaneously.
Sewing a French Seam
If you want a completely enclosed seam with no raw edges visible at all, a French seam is the cleanest option. It’s ideal for lightweight and sheer fabrics where the inside of the garment might show through.
Start by placing your fabric pieces with their wrong sides together (the opposite of a normal seam). Stitch 1/8 inch from the raw edge. Open the fabric and finger-press the seam flat on the wrong side. Now fold the fabric so the right sides face each other, with the seam you just sewed sitting right at the folded edge. Stitch again with a 1/4-inch seam allowance. This second line of stitching completely wraps the raw edges inside a neat tube of fabric. When you open the finished seam, no raw edge is visible from either side.
Fixing Skipped Stitches and Puckering
Skipped stitches are almost always a needle problem. The most common cause is using the wrong needle type for your fabric. A sharp quilting needle on jersey, for instance, will skip because it pierces the knit fibers instead of sliding between them. Switch to a ballpoint needle for stretchy fabrics.
A dull or bent needle causes the same issue. Needles dull faster than most people expect. A good rule of thumb is to swap in a fresh needle after about eight hours of sewing, or sooner if you’re working with heavy materials like canvas that wear the point down quickly. If your needle isn’t seated correctly in the machine (inserted the wrong way, slightly rotated, or not pushed all the way up), the bobbin hook can’t catch the top thread properly. Pull the needle out and reinsert it firmly.
Lint buildup inside the machine is another culprit. Thread sheds tiny fibers that pack around the bobbin case and feed dogs, eventually interfering with the mechanics. Use the small brush that came with your machine to clean these areas regularly.
Seam puckering typically comes from tension that’s set too high, a stitch length that’s too short for the fabric, or pulling the fabric through the machine instead of letting the feed dogs move it. Let the machine do the work. If puckering persists, try lengthening your stitch slightly and loosening the upper tension by one increment at a time.