How to Sew Straight Seams

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Do you struggle with sewing straight?

You think you’re sewing straight.

You’re trying to sew straight.

But when you remove the fabric from your sewing machine, the seam allowance isn’t even.

crooked seam allowance

Seam vs. Seam Allowance

First, let’s make sure we’re talking about the same thing.

A seam is a stitched line that joins two or more pieces of fabric.

The space between the edge of the fabric and the seam is the seam allowance.

1/2 inch seam allowance
The seam is sewn in blue thread. The seam allowance is 1/2-inch.

Typically, a pattern or project will call for a specific seam allowance.

For example, the seam allowance on clothing is often 5/8 of an inch, but the seam allowance for machine-pieced quilt blocks is 1/4-inch.

When I create my own projects, I frequently use a 1/2-inch seam allowance.

In the end, the specified seam allowance doesn’t matter because if the stitch line isn’t straight, the seam allowance won’t be even.

There are many different scenarios that could be the culprit of an inaccurate or wonky seam.

  • It could be hard-to-see measurement lines on the needle plate.
  • Or shadows cast over the sewing area so there isn’t enough light to see what you’re doing.
  • Maybe you’re sewing too fast and you lose some control over the fabric.

Never fear, regardless of the cause, there are solutions so you can sew straight seams every time.

Why Stitching Guidelines Aren’t Enough

Most needle plates have stitching guidelines etched into the metal.

These guidelines are a starting point for seam allowances.

However, many are not very long and can be difficult to see when you’re actually sewing.

This means they’re not the best to use as a guide for sewing a straight seam.

stitching guidelines on needle plate
These guidelines aren’t much longer than the presser foot.

Thankfully, there is a way to extend the stitching guidelines so you can sew a straight seam.

In addition, there are other tools you can use, too.

The methods described below are all ways I use to make sure seams are straight so seam allowances are accurate.

Tools to Sew a Straight Seam

Painter’s or Washi Tape

Use a piece of painter’s tape to extend the stitching guideline from the needle plate. The painter’s tape doesn’t leave a residue when it’s peeled off. Also, the bright color of the tape provides a contrast to the sewing machine’s color so the line you need to follow is easy to see.

Washi tape is an alternative to painter’s tape. It doesn’t leave anything sticky behind and it comes in many fun colors and patterns.

painter's tape as a guide
Painter’s tape is used in this image to provide a guide for a straight sewing line.

The only disadvantage I’ve had when using this method is the painter’s tape needs to be removed when I need to get into the accessory box.

Update: January 2, 2021 – Judy provided a solution to getting into the accessory box if you use painter’s tape.

She said, “Simply slice the tape at the junction between the bed of the machine and the accessories box. This allows access to the box without moving the tape.”

She also included a safety reminder to be careful when cutting the tape. You can see her solution in its entirety in the comments below.

A Presser Foot With Adjustable Guide

There is a presser foot with an adjustable built-in guide.

While this foot can be purchased separately, it does come with some machines. Check the presser feet that came with your machine to see if this little gem is there.

presser foot with an adjustable guide

If your machine didn’t come with an adjustable guide presser foot, when you shop for one, make sure it is compatible with your machine.

While a presser foot with an adjustable guide is a great tool, the ones I’ve seen don’t go as narrow as a 1/4-inch.

1/4-Inch Presser Foot

One of the golden rules of machine piecing quilt blocks is to use a quarter-inch seam allowance.

I can’t emphasize enough that the 1/4-inch presser foot is a must-have if you are piecing together quilt blocks on your sewing machine.

quarter inch presser foot

If you’re working on anything quilt related, make sure you have 1/4-inch presser foot and use the edge of the presser foot as the guide.

Tip for Getting 1/4″ Seam Allowance

One of the readers of my newsletter, Snappy Scissors, sent in this recommendation for getting the elusive 1/4-inch seam allowance on quilt blocks.

From Leigh Anne:

“To achieve an accurate [quilt] block, the seam should be sewn a scant 1/4-inch or 1-2 threads short of 1/4-inch. The process of pressing open or to one side takes up a thread or 2 of additional fabric. This occurs with each seam sewn so the more seams in the block the smaller it gets.

I use a tool from Perkins Dry Goods called the Perfect Piecing Seam Guide and a product from C&T Publishing called Sewing Edge: Reusable Vinyl Stops for Your Machine. This is a removable vinyl stop that with the Seam Guide is so easy to apply and remove when it’s in the way. I cut mine into 3 sections so I can easily remove my bobbin cover or extension table without removing the sewing edge.”

Edge of Standard Presser Foot

Sometimes a project doesn’t call for a specific seam allowance. This frequently happens to me when I’m creating something without a pattern or written directions.

In this situation, I will often use the edge of the standard presser foot as my guide for sewing a straight line.

use edge of presser foot for a guide

Tip: The edge of the standard presser foot works well on topstitching, too. I’ve even used the edge of the feed dogs to keep topstitching straight.

Removable Seam Guide

There are a variety of removable seam guides that can be purchased.

The two removable seam guides I have are:

The 6-in-1 Stick and Stich Guide uses a sticky adhesive to attach to the needle plate and can be used as a guide for straight and curved seams. It’s easy to remove and doesn’t leave a residue on the needle plate. When the adhesive becomes less sticky it can be renewed with water and dishwashing soap.

removable seam guide with adhesive on the bottom

The magnetic seam guide attaches to the needle plate with a magnet. Note: If your machine has computerized parts, you may not want to use the magnetic seam guide.

removable seam guide with magnet on the bottom

Both removable seam guides work well and help you achieve an accurate seam allowance.

However, if you’re using pins or clips, it’s important to pay attention and remove them before they get caught on the guides.

Tips to Sew a Straight Seam

Regardless of the tool you use as a guide to sew a straight seam, there are a few tips that make a big difference.

Light Up the Sewing Area

Too many shadows in the needle and presser foot area may make it difficult to see the guide you’re using to sew straight.

If you’re unable to light up the area enough to eliminate shadows with a tabletop or stand lamp, consider getting:

  • a removable lamp that attaches to your sewing machine and has an adjustable neck
removable light for sewing machine
This OttLite is removable. It slides into a bracket that is attached to my machine with an adhesive strip.
flexible LED light strip
This LED light strip has an adjustable dimmer switch to allow you to adjust the brightness.

Sew Slower

The speed you sew can affect how straight a seam is. The faster you sew the greater the chance the seam will not be entirely straight.

Sewing isn’t a race.

To make sure the seam is as straight as possible, ease up on the foot control to slow down.

Don’t Watch the Needle

The up and down of the needle can be mesmerizing.

And, if you’re new to sewing, there may be a little fear you’ll sew over your finger if you take your eyes off the needle.

If you keep your hands placed in front and to the side of the needle plate, you won’t pierce your finger.

To sew a straight seam, you need to look at the guide you’re using, not the needle.

Keep your eyes on the edge of the fabric so you know it’s moving along the guide as it goes through the sewing machine.

How to Sew Straight Seams

These 8 tools and tips will help you sew straight seams resulting in accurate seam allowances.

There isn’t one tool or strategy that is better than another.

It really depends on the type of project you’re working on and what best meets your needs at that time.

Remember, the goal is always to sew as straight as you can.

When you sew straight, seam allowances are accurate.

As a result, you will be satisfied with the overall appearance of the finished project.

Let’s Connect

My goal at The Ruffled Purse is to support, empower, and inspire you to sew and make wonderful things for yourself, your home, and others.

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  1. A little hint that might help beginners. . . .
    After you have carefully attached painters tape to accurately stitch a seam and need to get into the accessories box don’t remove the tape. Simply slice the tape at the junction between the bed of the machine and the accessories box. This allows access to the box without moving the tape. Be sure to be cautious with any sharp implement so as to keep from damaging the machine or yourself. Works for me!

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