Learning how to sew a seam is one of the first and most important sewing skills for beginners. Nearly every sewing project — from garments to cushions and bags — relies on sewing strong, straight seams correctly. This beginner-friendly tutorial will show you how to sew a seam both by machine and by hand, including tips for straight seams, curved seams, knit fabrics, and specialty seam finishes.

What is a Sewing Seam?

A seam is the line where two pieces of fabric are stitched together. Seams are the foundation of sewing and are used in clothing, bags, quilting, home decor, and crafts. Strong, accurate seams improve the fit, durability, and appearance of your sewing projects. Mastering straight seams is one of the fastest ways for beginner sewers to improve their skills.

Sewing seams correctly helps:

• prevent garments from falling apart
• improve fit and construction
• create a professional-looking sewing
• reduce puckering and fraying

Seam allowance is the distance between the stitching line and the raw edge of the fabric. Most sewing patterns use 1/2 inch (12mm) or 5/8 inch (15mm). Using the correct seam allowance is important because it affects the final size and fit of your sewing project.

How to Sew a Seam by Machine (Step by Step)

To sew a seam with a sewing machine, you will need:

• 2 scraps of fabric. I like using 5 x 5 inch (12 x 12cm) pieces as they are easy to handle.
• Thread
• Your sewing machine
• Pins
• All-purpose sewing foot: This is your regular straight stitching foot that comes with your machine. It is usually all-metal or half-metal and half-plastic. On most modern machines, it will snap on, but older machines may have a screw mechanism for attaching.

If you haven’t purchased your sewing supplies yet, then read my article on beginner sewing kits on a budget to find out the best basics to start with.

Further Reading:

• Types of Thread
• How to Thread a Sewing Machine
• How to Wind a Bobbin

1. Pin the Fabric

Pin your two pieces of fabric with the RIGHT sides together at the raw edge. This means the right sides (correct sides or printed sides) will be facing each other. If you are using plain fabric, it may not have a right or wrong side. Other fabrics will be faded at the back, so it will be obvious which is the right and wrong sides.

I like to use the horizontal method of pinning as I find it faster to remove. This means the pins are placed vertically along the edge, with the heads sticking out from the fabric. It is a personal preference as to which way you place the pins.

Once you get confident with sewing seams, you will probably be able to sew a straight seam without pins. An alternative to using pins is to hand-baste the seam with an up-and-down running stitch. This will hold the fabric pieces in place without you having to worry about sewing over pins and breaking a needle.

2. Set the Seam Allowance

Refer to your pattern instructions to find out what your seam allowance is. This is the distance you will be sewing from the edge. Common seam allowances are 1/2 inch (12mm) or 5/8 inch (15mm).

If your pattern does not have a seam allowance (this is common for European patterns), you will need to add it yourself. Don’t worry, I have an entire article on seam allowances and how to add them.

Place your fabric under the foot with the needle on the seam allowance line and hold the threads. You should start at least 1/4 inch (6mm) from the edge so that the whole foot is on the fabric. The reason you should hold the threads to the back is so they don’t get caught under the foot or in the machine. You will only be holding them at the start, not the whole time you are sewing.

You don’t need to measure the seam allowance. Most machines have markings on the metal plate or in front of the foot, so you can align the edge of the fabric with them. On my machine, the measurements are in inches on the metal at the back, and you can see the millimeters on the front plastic.

3. Backstitch

Set your stitch length to 2.5. This is a good average setting to test on your fabric and is good for sewing pants, cuffs, collars, and more. The width should be 0 since we are doing a straight stitch.

Still holding the threads, backstitch almost to the edge. This simply means you take a few stitches backward. There is normally a button on the front of your machine to go backward. When the button is pressed, it sews backward, and when it is released, it sews forward. Don’t go off the edge. Most likely, this backstitching will only be 3 or 4 stitches. This is enough.

How to Sew a Seam at the Ends – Back stitching will stop the ends from unraveling, making your seam much stronger under stress.

4. Stitch Forwards

Stop backstitching, then release the threads in your fingers and start stitching forward. Start sewing forward in a straight line along the stitching line of the seam allowance line. Use the guides in the needle plate to keep it nice and straight.

5. Backstitch the End

Backstitch the end of the seam as well. Stop 1/4 inch (6mm) from the edge, press the back button and take a few stitches backward. To remove the fabric from the machine, lift the foot and make sure the needle is up. Pull the fabric out and cut the threads. If your needle is down, you can turn the handwheel on the side of the machine to slowly lift it up.

6. Press the Seam

Open up your piece, press, and there it is. A nice straight seam! Pressing for sewing is slightly different from your regular ironing. Instead of dragging the iron along the seam, press up and down with medium pressure.

Tips for Sewing Straight Seams

Keeping seams straight becomes easier with practice. Many beginners find painter’s tape useful as an extra seam guide. Helpful beginner tips include:

• watching the seam guide instead of the needle
• sewing slowly
• pressing fabric first
• pinning carefully
• practicing on scraps

Troubleshooting Sewing a Seam

If your stitches look loopy on the back or the front, it may be because the sewing machine tension is incorrect. Adjust it so the top and bottom threads are perfectly balanced.

Our lesson on how to sew a seam by machine is finished, and now let’s get on to how to sew a seam by hand.

How to Sew a Seam in Knits

Sewing knits with a machine is almost the same as sewing woven fabrics, with one exception. Instead of a straight stitch, use a narrow zigzag stitch. The reason a zigzag is better is that it stretches with the fabric, preventing stitches from popping.

How to Sew a Seam with Curves and Corners

Sewing gentle curves is easy when you gently swing the fabric around as you sew. It is best done in one motion with your machine on a slow-speed setting. If you don’t have speed settings, then put your foot down lightly to sew.

Sharper curves may require you to stop and lift the presser foot to release bunched-up fabric. Put the presser foot down and start sewing again. The sharper the curve, the more times you will need to do this. For really tight curves, you may need to use the handwheel to move the needle even more slowly.

Corners are easier to sew than curves. Stop at the curve, lift the presser foot, pivot, and put the foot back down again.

Specialty Sewing Seams

There are many types of sewing seams designed for different fabrics and sewing projects. Some seams focus on strength and durability, while others create decorative or professional finishes. Common seam types include plain, French, flat-felled, open, and closed seams. If you want to learn the differences between all seam types, read the full types of Seams guide.

How to Sew a Seam by Hand

I have a longer article on how to hand stitch a seam, but here I will give you a rundown on the best 3 methods. How to sew a seam by hand can be done by using:

1. Running Stitch
2. Backstitch
3. Ladder Stitch (Invisible Stitch)

Supplies for Hand Sewn Seams

To sew a seam by hand, you will need:

• FABRIC – 2 scraps of fabric.
• THREAD – The best type of thread to use is a polyester thread that is designed for general purposes.
• NEEDLES – Universal needles are general sewing needles suitable for a wide variety of fabrics. Choose a needle size appropriate to your fabric.
• PINS

Running stitch is a simple up-and-down stitch, and if you are a complete beginner, then this is going to be the best stitch for you to learn how to sew a seam. It is one of the most basic stitches. Start by threading your needle with a double thread and knotting the end. If you have any trouble threading the needle, read my article on how to thread a needle.

Piece through the fabric from the underside and take small up and down stitches. For sewing a seam your stitches should be no more than 1/4 inch (6mm) apart. The smaller the stitches, the stronger your seam will be.

Backstitch

Once you have mastered the running stitch, you will want to upgrade to the backstitch. Backstitch is an extra-strong hand stitch suitable for hand-stitched seams. It is also a useful embroidery stitch for decorative sewing. Read the full tutorial on how to backstitch

Invisible Ladder Stitch

For seams that have split open and need repairing, a ladder stitch can create an invisible seam, particularly when stitched in a matching thread. This invisible stitch is handy for closing cushion seams and mending toys.

• Bring the needle up through the fold of the seam at (1). This will hide the knot inside.
• Cross to the other side of the seam and insert the needle along the fold from (2) to (3).
• Cross over again and insert the needle from (4) to (5) along the fold of the seam.
• You can see the ladder starting to appear. Gently pull tight and you will have an invisible seam. Even with the bright red contrasting thread you can hardly see the stitches. Smaller stitches will hold a stronger seam.

More Types of Seam Hand Stitches

Here are some more hand stitches that can be used for sewing seams.

• Blanket Stitch Tutorial – Perfect for the edges of blankets
• Whip Stitch – Is commonly used for seams in felt
• Catch Stitch – Can be used to sew hems and edges

Common Sewing Seam Mistakes and Tips

Common Mistake	Tip for Better Results
Sewing without backstitching can cause unraveling.	Always backstitch at the beginning and end of seams.
Uneven seam allowances may affect garment sizing.	Follow machine seam guides carefully while sewing.
Pulling fabric while sewing can distort seams.	Allow feed dogs to move fabric naturally.
Skipping pressing steps reduces seam quality.	Press seams after sewing for a professional finish.
Straight stitches on stretch fabric may cause popping.	Use zig-zag or stretch stitches on knit fabrics.
Sewing curves too quickly can create puckers.	Sew slowly and pivot the fabric gradually.
Loose thread tension creates messy stitches.	Test and adjust machine tension on scraps first.
Long stitches for delicate seams may weaken it.	Adjust stitch length according to fabric type.

How to Sew a Seam – The Next Step

After you have learned how to sew a seam, the next step is to finish the seam to prevent the edges from fraying. One of the easiest ways to do this is to use pinking shears to cut the edge. This serrated edge will help lessen fraying. A serger can also be used and gives a professional-looking seam. If you don’t have a serger, a wide zigzag stitch is an easy alternative to a serged seam. Read my article on seam finishes for more easy techniques.

How to Sew a Seam FAQs

Pin for Later

How to Sew a Seam – In Conclusion

Congratulations! You’ve sewn your first pieces and now know how to sew a seam. With a little practice, you will now be ready to tackle your first sewing project and your first straight seam. Go and have a practice on some scraps and tell me what you think. Learning straight seams, curved seams, and proper seam finishes creates the foundation for almost every sewing technique you will use in the future.

More Sewing for Beginners

• Seam Finishes – 6 ways to finish a seam
• How to Sew a Hem: 5 ways 
• How to Use a Seam Ripper
• Basic Machine Stitches
• Sewing 101
• Seam Allowance