Machine embroidery thread weights and types

What thread weight means

Embroidery thread weight is a length-to-mass measure, not a measure of how heavy the thread feels. The common weight system describes how many kilometers of thread weigh one kilogram, so a higher number means a finer thread. A 60 wt thread is thinner than a 40 wt, and a 30 wt is thicker than a 40 wt.

Different makers sometimes use other systems, such as denier or tex, and the same nominal weight can vary a little between brands. Treat the weight as a guide and stitch a test on scrap fabric when you switch brands, especially on dense designs.

Why 40 wt is the standard

Commercial and built-in embroidery designs are usually digitized with 40 wt thread in mind. The stitch density, the spacing between rows in fills and the width of satin columns all assume that thread thickness. Stitching a design in 40 wt gives the coverage the digitizer intended, with no fabric showing through and no excess bulk.

If you switch to 30 wt on the same design, the stitches pile up and the design can become stiff, heavy and prone to thread breaks. If you switch to 60 wt, the fabric may show through fills. When you want to use a different weight, choose designs made for it or adjust the density in your embroidery software.

Rayon versus polyester embroidery thread

Rayon is made from regenerated cellulose. It has a soft, high sheen and runs smoothly, which is why it has long been a favorite for decorative work. It is weaker than polyester, it can lose color with chlorine bleach, and it may break more often at high speed.

Polyester embroidery thread is a trilobal filament with a sheen close to rayon. It is stronger, holds up to bleach and frequent washing, and is the common choice for children's clothing, towels, uniforms and anything that will be washed hard. Most home embroiderers find polyester the easier default.

Both run on any home embroidery machine with a 75/11 embroidery needle. If you are getting fraying or snapping, the fiber is rarely the only cause; see why embroidery thread shreds and breaks.

Bobbin thread for machine embroidery

Embroidery uses a separate, much finer bobbin thread, commonly sold as 60 wt or 90 wt, usually in white or black. Because it is thin, more of it fits on a bobbin and it adds little bulk to the back of the design. The top thread tension is set so a small amount of the top color pulls to the underside, and the fine bobbin thread stays hidden under the design.

You can buy bobbin thread on cones and wind your own, or buy prewound bobbins. Make sure prewound bobbins are the right class and size for your machine, since bobbins that look similar may not fit. The bobbin size chart lists the common types.

Do not use regular 50 wt sewing thread in the bobbin for embroidery. It is thicker, fills the bobbin faster, adds bulk and can upset the tension balance so bobbin thread shows on top. If you do see white bobbin thread on the front, check the settings described in embroidery machine tension settings.

Note.Some machines have a separate bobbin case or tension setting for embroidery. Follow your manual if it specifies one.

60 wt thread for small lettering

Lettering under about a quarter inch tall is hard to stitch cleanly in 40 wt, because the thread is wide relative to the letters and small counters such as the inside of an e or a close up. A 60 wt top thread gives sharper edges on small text and fine line work.

Pair 60 wt with a smaller needle, often a 65/9 or 70/10, or keep a 75/11 on slightly heavier fabric. Use designs digitized for fine thread, or reduce the density in software, and slow the machine down if you see breaks.

Specialty threads: metallic, cotton and wool blends

Metallic thread adds shine but is less forgiving. Use a metallic or topstitch needle in 80/12 or 90/14, put the spool on a separate thread stand if it twists, lower the speed and loosen the top tension slightly. Choose simpler designs without very short, dense stitches.

Cotton embroidery thread has a matte finish suited to quilts and vintage looks. It produces more lint than polyester, so clean the bobbin area more often. Wool blend and 12 wt threads give a hand-stitched look and need a large needle and designs made for heavy thread.

If you are still setting up, the machine embroidery needle guide explains which needle to pair with each thread, and our needle and thread finder gives a quick answer for any fabric.

• Metallic: metallic or topstitch needle, slower speed, thread stand.
• Cotton: 75/11 or 90/14, clean lint often.
• 30 wt or 12 wt: 90/14 or larger, designs digitized for heavy thread.

Compare sewing and embroidery combos →

Frequently asked questions

What weight thread does a Brother embroidery machine use? Brother home embroidery machines are set up for 40 wt embroidery thread on top and a fine embroidery bobbin thread underneath. The built-in designs assume 40 wt, so start there.

Is a higher thread weight thicker? No. In the common weight system a higher number means a finer thread. A 60 wt is thinner than a 40 wt, and a 30 wt is thicker.

Can I use regular sewing thread for machine embroidery? You can for a test, but all-purpose sewing thread has less sheen and is usually thicker than 40 wt embroidery thread, so fills look dull and can become dense. Use proper embroidery thread for finished work.

Do I need to match the bobbin thread color? Usually no. White or black bobbin thread is standard. Match the bobbin to the top only when both sides will show, such as on towels or free-standing lace.