How To Adjust Stitch Length On A Sewing Machine: A Complete Guide
The stitch length is one of the most important settings on a sewing machine. It affects the appearance, strength, and functionality of the stitches you sew. Learning how to properly adjust stitch length is crucial for any sewing project. In this comprehensive guide, you’ll learn everything you need to know about stitch length and how to adjust it on your sewing machine for perfect results every time.
What is Stitch Length?
Stitch length refers to the distance between two consecutive stitches sewn by your machine. It is measured in millimeters (mm) on most modern sewing machines. Stitch length numbers usually range from 0 to 5 mm, with some machines going up to 7 mm.
On older, vintage sewing machines, stitch length was indicated in stitches per inch (SPI). These machines had stitch length settings from around 4 to 60 SPI. The higher the number, the shorter the stitch, since more stitches could fit within an inch.
You can convert between mm and SPI using the following simple formulas:
- Stitches per inch = 25.4 ÷ Stitch length in mm
- Stitch length in mm = 25.4 ÷ Stitches per inch
For example, if your pattern calls for a stitch length of 10 SPI, you would calculate:
25.4 ÷ 10 SPI = 2.5 mm
If your machine setting reads 3.5 mm, you would calculate:
25.4 ÷ 3.5 mm = 7.25 SPI (round to 7 SPI)
Understanding these conversions allows you to translate stitch length between metric and imperial measurements.
Image suggestion: Infographic showing stitch length examples in mm and SPI
How to Adjust Stitch Length
The way you adjust stitch length depends on the type of sewing machine you have: mechanical, electronic, or computerized. Here’s how to find the controls on each:
Mechanical sewing machines – Look for a dial on the front of the machine, labeled either “Length” or with a dashed line symbol that goes from short to long. Turn the dial to the desired number to set the stitch length.
Electronic sewing machines – There will be a LED display with a stitch length indicator light next to the stitch length icon (often a dashed line). Use the + and – buttons to increase or decrease length.
Computerized sewing machines – Find either a stitch length section on the LCD touchscreen display, or buttons labeled with a stitch length icon to press to adjust up and down.
Image suggestion: Photo of stitch length controls on different machine types
When you increase the stitch length, more fabric is pulled under the presser foot before the needle punches down again. This makes each stitch longer. Decreasing length pulls less fabric per stitch, making stitches shorter.
Recommended Stitch Lengths
Here is a table of recommended stitch length settings for different fabrics and sewing purposes:
| Purpose/Fabric | Stitch Length (mm) | Stitches Per Inch |
|---|---|---|
| Basting | 5.0 – 7.0 | 4 – 5 |
| Stay Stitching | 1.5 – 2.0 | 12 – 16 |
| Lightweight Fabrics | 1.5 – 2.5 | 10 – 16 |
| Medium Fabrics | 2.0 – 3.0 | 8 – 12 |
| Heavyweight Fabrics | 3.0 – 4.0 | 6 – 8 |
| Topstitching (light/medium) | 3.0 – 3.5 | 7 – 8 |
| Topstitching (heavy) | 3.5 – 4.0 | 6 – 7 |
| Quilt Piecing | 1.8 – 2.0 | 12 – 14 |
| Machine Quilting | 2.5 – 3.5 | 7 – 10 |
| Knit Fabrics | 2.5 – 3.5 | 7 – 10 |
These are general guidelines only. It’s always best to test your stitch length on a scrap of the actual fabric you’re using before sewing your project.
Shorter stitches are great for lightweight fabrics to prevent puckering. Longer stitches work better on heavy fabrics so the needle can pierce the layers. Adjust as needed for your purpose – shorter for seams/construction, longer for decoration.
Adjusting Straight Stitch Length
For straight stitches, the most common adjustment you’ll make is to the stitch length. The length setting controls both the appearance of the stitch and the strength.
For basting, use the longest stitch length. This makes the stitches easier to remove later. When sewing lightweight fabrics like silk, use a shorter length to prevent puckering along the seam line.
Image suggestion: Photo showing a straight stitch with different length settings
Setting the stitch length to the shortest possible will sew a tiny locked stitch. This is useful for anchoring the stitching without having to backstitch.
Always test your straight stitch on a scrap of your fabric doubled over to mimic a seam. Check tension hasn’t changed based on fabric and adjust length until you achieve smooth, even stitching.
Adjusting Zigzag/Decorative Stitch Length
In addition to straight stitches, you can adjust the length of zigzag, satin, and decorative stitches on your machine. This dramatically affects the appearance and function of these stitches.
For zigzag stitches, adjusting the length changes how open or closed the points of the zigzag are. Lengthening produces a more open shape, while shortening closes it up.
Image suggestion: Zigzag stitch example with different lengths
Try different length settings on scraps when using decorative stitches. Many machines default to 2.5 mm, but you may prefer a shorter or longer length for certain stitches.
Length is also very important for satin stitches used in buttonholes or applique. Test on your fabric doubled over to mimic the layering. Adjust until the stitch looks proportional without gaps.
Adjusting Stitch Width
In addition to length adjustments, you can also adjust the width of zigzag and decorative stitches.
For straight stitches, adjusting the width will move the needle position left or right. This allows you to line up stitches with different machine seam guides.
Image suggestion: Straight stitch with different width settings
For zigzag and decorative stitches, adjusting the width changes how wide the stitch pattern is. Lengthening the zigzag width makes the stitch stretchier. Adjusting the width of decorative stitches changes the overall size of the design.
Always test stitch width adjustments on scrap fabric too. Changing the width may also require adjustments to the length to keep the stitch looking proportional.
Troubleshooting Uneven Stitches
Sometimes you may encounter problems with your stitching, even after adjusting the length. Uneven, wavering stitches are often caused by:
- Pulling or pushing the fabric through instead of letting the feed dogs advance it correctly. Avoid forcing the fabric.
- Low presser foot pressure so feed dogs can’t grip fabric firmly. Increase pressure slightly.
- Incorrect upper thread tension. Check threading and increase/decrease tension.
- Using an inappropriate length for the fabric. Heavy fabrics need longer stitches.
Image suggestion: Photo showing even vs uneven stitches
For sewing fabrics of varying thickness, a walking foot will help feed the layers evenly. Test stitch length in the thickest part of your fabric when adjusting.
Always start by checking if stitch issues occur when using just a single layer of fabric. If the problem only appears in thicker or denser fabric, experiment with length, tension, and presser foot pressure to get uniform stitches. Slowing your sewing speed can also help.
Conclusion
Learning how to adjust stitch length properly can take some practice, but it’s a skill that will allow you to sew all kinds of fabrics and produce professional finished seams and decorative stitching.
Follow the stitch length recommendations provided in this guide as a starting point. Always test your settings on scraps of your actual project fabric before sewing your garment or quilting your quilt. Be prepared to tweak the settings until you acheive smooth, even stitching with the correct appearance.
With some experimenting, you’ll soon be adjusting your stitch length like a pro for any sewing project! Refer back to this article if you ever run into wavy, uneven stitches and need help getting them back under control.