How to Sew Straight (Seams, Hems, Topstitch) – 8 Proven Tips

Sewing in a straight line is often the first challenge new sewists face, so today I’ll share 8 of my best tips for helping you sew perfectly straight and accurate seams, hems, and topstitching.

The easiest way to sew in straight lines is to use a presser foot with a built-in guide. However, if you don’t have one, a combination of watching the seam allowance lines as you’re sewing and going very slowly should do the trick. If you’re sewing a short distance, you can also mark the stitching line directly on your fabric using a marking tool and a ruler so that you can simply follow the line as you sew. 

If you just got your sewing machine and you’re trying to sew a straight line for the very first time, stick around to the end where I’ll guide you through the whole process from turning your machine on to trimming the threads at the end. You can also use the links below to jump to the relevant sections:

Tips for sewing straight: 

  1. Use a presser foot with a built-in guide
  2. Use a seam allowance guide
  3. Draw the stitching line on your fabric
  4. Have a straight, clean-cut edge on your fabric
  5. Watch the seam allowance guide, not the needle
  6. Sew slowly
  7. Use your hands to guide the fabric
  8. Tips for sewing a straight hem

How to sew a straight line for the first time: Step-by-step tutorial (+Video)


Tip #1: Use a presser foot with a built-in guide

Presser foot with adjustable guide:

These presser feet feature a ruler extending out from the right side of the foot. By using the sliding plastic guide attached to the ruler, you can adjust the exact width of the guide to match your chosen seam allowance and sew a consistently straight line. This is useful for sewing seams.

Uses: Sewing with the seam allowance of your choice, sewing wide hems, topstitching. 

¼” foot with a guide:

¼” presser feet have a 6 mm / ¼” distance between their central needle hole and their outer edges. By aligning the edge of the fabric with the edge of the presser foot, you can achieve an exact 6 mm /  ¼” seam allowance. Some versions come with an edge guide to stop the fabric from going past it – this is the one I recommend if you care about precision. The width is not adjustable so it’s not ideal for sewing regular seam allowances that are 3/8″ – 5/8″ wide.

Uses: This foot is most often used by quilters, as most piecing is done with precise 6 mm / ¼” seam allowances in quilting. You can also use it for achieving a parallel and straight topstitching line that’s 6 mm / ¼” away from the seam line.

Stitch-in-the-ditch / edge-stitching / edge-joining foot:

These feet feature an additional metal or plastic blade-like guide in the middle of the foot that extends down. This blade slots into the ditch formed by your seam, helping you guide the fabric exactly along the seam line.

Uses: ‘Stitching-in-the-ditch’ to attach bindings, facings, cuffs, waistbands, etc. Edge stitching. Under stitching. Topstitching. Hemming. It’s not useful for sewing a normal seam.

If you don’t have a foot with a guide, use the Standard foot:

A standard presser foot (aka. zig zag foot) will come with your machine. It has a width of 8 mm between the central needle position and the outer edge of the foot. If you move your needle 2 mm to the left or choose the left needle position on your machine, this will give you an exact 1 cm / ⅜” distance between the needle and the right edge of the foot. By aligning the edge of your fabric with the right outer edge of the presser foot, you can achieve a perfect 1 cm / ⅜” seam allowance. Alternatively, by moving the needle 2 mm to the right or by choosing the right needle position, you can achieve a 6 mm / ¼” seam allowance.

Uses: Sewing with 1 cm / ⅜” or 6 mm / ¼” seam allowances.

Pros: 

  • They are very easy to use, and you’ll most likely succeed on your first couple of tries.

Cons: 

  • If your sewing machine didn’t come with these feet, you’ll need to spend extra to get them. They can cost anywhere between $5-25, depending on the brand and model of your sewing machine. 
  • There’s no ‘one foot fits all’. Each foot is only useful in specific situations. Eg. a stitch-in-the-ditch foot is great for the stitch-in-the-ditch technique and topstitching, but useless for sewing normal seams.

How to use them:

  1. Attach your presser foot of choice to your sewing machine. 
  2. Align the edge of your fabric with the edge of your presser foot. This step may look a bit different depending on which presser foot you’re using:
    1. If you’re using a standard foot, align the fabric with the edge of the foot and then move the needle to the left or right to achieve a ¼” / 6 mm or ⅜” / 1 cm seam allowance.
    2. If you’re using a ¼” foot, simply align the edge of the fabric with the edge of the presser foot.
    3. If you’re using a presser foot with an adjustable guide, first move the sliding guide to your chosen seam allowance number. Next, align the edge of the fabric with the inner edge of the guide.
    4. If you’re using a stitch-in-the-ditch foot, place the blade of the foot into the ditch formed by the seam, and move your needle to the left or to the right to topstitch, or leave it centered for stitching in the ditch.
  3. Select a straight stitch with a length of 2.5 and a tension of 4-5, which are the default settings on most domestic sewing machines.
  4. Start sewing, and make sure you keep the edge of the fabric aligned with the edge of your presser foot or guide.

Tip #2: Use a seam allowance guide

Description:

The most basic way to achieve straight lines when sewing is to follow some sort of seam allowance guide. There are a few different types of seam allowance guides you can use: 

  • Your sewing machine most likely has markings on the needle plate (which is the metal plate under the needle). There will be lines engraved into the metal plate which represent common seam allowances like ⅜”, ½”, ⅝”, or 1 cm, 1.2 cm, 1.6 cm. Pick a line that matches your desired seam allowance and line up the edge of the fabric with that line. Make sure it stays on that line whilst you sew.
  • If you’re finding it hard to keep track of which line of the needle plate you’re supposed to follow or if you’re using an uncommon seam allowance, you can place some masking tape on the exact distance you like. To do so, measure your preferred seam allowance from the needle to the side and place the inner edge of the washi or masking tape on that spot.
  • Alternatively, you can stick a stack of Post-it notes on the seam allowance line of your choice. This creates a barrier stopping your fabric from going past the correct seam allowance.
  • You can also buy a magnetic seam guide. They magnetically attach to your needle plate and you place them along your chosen seam allowance line. This creates a barrier that stops your fabric from going past it. Some machines have a part-metal and part-plastic plate so the guide may not ‘stick’ to these properly.
  • Another quick way to make a seam allowance guide at home is to tie or sew a piece of wide elastic to form a circle and slide it on your sewing machine’s bed. You can then adjust its position so that it rests on the right of your preferred seam allowance. Make sure the elastic is on snugly so that it doesn’t shift out of place as you sew.

Pros: 

  • The stack of Post-its and the magnetic guide form a physical wall that the fabric can’t go past, so it’s really easy to keep your fabric aligned with the guide. The elastic trick is also similar in that it has some thickness to it, but the former two options have more height so it’s easier to stay within the lines.

Cons: 

  • The seam allowance markings and the washi tape are flat on the needle plate, meaning they don’t have the 3-dimensional projection that the stack of Post-its and the magnetic guide have. This means you’ll have to be more careful to keep your fabric aligned with these guides, and it may take some time and practice to get it perfect.

Uses: 

  • Sewing seams.

How to do it:

  1.  Select the seam allowance guide of your choice from the list above.
  2. Align the right edge of your fabric with the guide.
  3.  Select a straight stitch. The standard settings are a stitch length of 2.5 and a tension of 4-5.
  4. Sew by keeping an eye on the guide. The fabric should be just touching the guide the entire time you’re sewing.

Tip #3: Draw the stitch line on your fabric

Description:

One of the most guaranteed ways to achieve a straight stitch is to draw the stitch line directly on your fabric and then follow the marking as you sew. This is best suited for shorter lines of stitching, as it can be too time-consuming on longer lengths of fabric.

Pros: 

  • Easy to do.
  • Doesn’t require much special equipment (just temporary fabric markers like tailor’s chalk).

Cons: 

  • Time-consuming.
  • Best suited for small areas.

Uses: 

  • Sewing seams.
  • Top stitching.

How to do it:

  1. Lay your fabric in front of you. If you’re using this method to sew a plain seam, your fabric should be wrong-side up. If you’re using this method to do topstitching, your fabric should be right-side up.
  2. For seaming, use a clear quilting ruler and the fabric marking tool of your choice, and mark the seam allowance at the edge of your fabric. For topstitching, you can use a ruler or a paper template (if your topstitching forms a distinct shape, like the topstitching of the fly of trousers).
  3. Place your marked fabric under the needle on your sewing machine, and select a straight stitch with a center needle position, a length of 2.5 and a tension of 4-5, which are the default settings on most domestic sewing machines.
  4. Center the line you drew on your presser foot, and lower the presser foot.
  5. Carefully follow the line as you’re sewing. Focus on keeping the line centered on the presser foot.

Tip #4: Have a straight, clean-cut edge on your fabric

Description:

Having a clean cut at the edge of your fabric is really helpful in maintaining an accurate seam allowance and sewing in a straight line. If your fabric has jagged edges or lots of fraying, make sure you go back and trim off any uneven bits and fraying.

Pros: 

  • Simple to do.
  • Doesn’t require any special equipment.

Cons: 

  • If you’re working with a pattern, you may not have as much room to trim your fabric without compromising the accuracy of the measurements. Try your best to remove as little material as possible when doing this, or try to get a clean-cut edge on your first go at cutting the pattern pieces out.

How to do it:

  1. Using a pair of fabric scissors or a rotary cutter (and mat), trim a very small amount of fabric to neaten the edge.
  2. Next, follow any of the methods discussed in this article to sew your pieces together.

Tip #5: Watch the seam allowance guide, not the needle

Description:

Many beginner sewists make the mistake of watching the needle go up and down as they’re sewing, rather than keeping their eyes on the seam allowance guide. This makes it challenging to keep a straight line, as your eyes are trying to focus on a rapidly moving object. Instead, ignore the needle and watch the seam allowance guide on the needle plate, making sure the edge of your fabric doesn’t stray from the guide.

Uses: 

  • Sewing seams.
  • Sewing hems.
  • Topstitching.
  • And nearly all other situations.

How to do it:

  1. Place your fabric under the needle of your sewing machine as usual, and select a straight stitch with a length of 2.5 and a tension of 4-5 (these are the standard settings).
  2. Align the edge of your fabric with the seam allowance guide on the needle plate, or an alternative guide we discussed in Tip 2.
  3. Keep looking at the edge of your fabric as you sew and make sure it’s always aligned with your seam allowance guide. If the fabric starts to stray, stop sewing, readjust the fabric a tiny bit, and keep sewing slowly until you’re back on track.

Tip #6: Sew slowly

Description:

It might be tempting to go fast to quickly finish your sewing project, but simply slowing down will do wonders for your accuracy. Don’t be scared to take as many pauses as you need to make sure the fabric is still aligned with the guide you’re using and to readjust the position of your hands. Sewing slower or taking pauses will not negatively affect the quality of stitching.

If you have a computerized sewing machine with speed control, lower the maximum speed of the machine so that you’re forced to go slower. If your machine doesn’t have this feature, simply try to press the pedal as lightly as possible.

Uses: 

  • Sewing seams.
  • Topstitching.
  • Sewing hems.
  • And nearly all other situations.

Tip #7: Use your hands to guide the fabric

Description:

Learning how to use your hands effectively while operating your sewing machine is important. Different materials and techniques may require you to use your hands in a different way, but I’ll go over some of the basics here:

  • Place your left hand on the fabric, on the bed of your sewing machine. Keep it close to the needle and the presser foot. As you’re sewing, the feed dogs of your sewing machine will move the fabric along toward the back, and you’ll need to frequently reposition your left hand so that it’s near the needle. This is because you need to control the fabric before it gets stitched by the needle.
  • You can use your right hand to gently guide the fabric when it’s feeding into your machine. To do so, position your right hand in front of the needle at a good distance. Use this hand to make sure your two pieces of fabric are aligned at the edges and follow your seam allowance guide before they go under the needle.
  • Don’t pull or tug your fabric from the front or the back. This may cause tension issues, resulting in poor stitch quality, stretched-out fabric, and puckers. The fabric should remain nice and flat as it’s feeding through your sewing machine.

Uses: 

  • Sewing seams.
  • Topstitching.
  • Sewing hems.
  • And nearly all other situations.

#8: Tips for sewing a straight hem

  • I find that starting with a nicely pressed hem is massively helpful when sewing a straight hem. You can use a few different techniques for this step:
    • Mark your pressing guidelines on your fabric using a clear quilting ruler.
    • Use a seam gauge tool to frequently check you’re maintaining the same hem allowance as you’re pressing the hem up.
    • Alternatively, use a hot hemmer / hem gauge tool to quickly and accurately press your hem up.
    • If you’re working with a trickier fabric or wool, use a wooden tailor’s clapper to set the pressing into place.
  • You can also try hand-basting the hem into place either before or after pressing it up. This will securely stabilize the folds of the hem and stop the fabric from shifting.
  • I really like using a stitch-in-the-ditch / edge-stitching foot to achieve a straight line of stitching on my hems. Position the fabric so that the folded edge is aligned with the blade-like guide on the foot. Shift your needle 2-3 mm to the side, and sew using a straight stitch with a length of 2.5 – 3 and a tension of 4-5. 
  • You can also explore different presser feet that are designed to make hemming easier and neater, such as narrow and wide hemmer feet. To learn more about different presser feet for hemming, check out our article on 9 sewing machine feet for hemming.

How to sew a straight line for the first time (step-by-step tutorial):

If it’s your first time using a sewing machine, let’s walk through how to sew a straight seam to join 2 layers of fabric together. This will form the foundation of your sewing practice, as you’ll often need to sew straight seams in most sewing projects. When practicing, I recommend using a medium-weight woven cotton fabric with no stretch, as this is a stable fabric that’s easy to work with. For this tutorial, I’m using quilting cotton and assuming that you’re sewing with a ⅜” or 1 cm seam allowance, but feel free to use any seam allowance you like. 

  1. Start by preparing your sewing machine.
    1. Turn your machine on.
    2. Fill up the bobbin with thread.
    3. Insert the bobbin into your machine.
    4. Thread the needle.
    5. (If your machine requires you to do so) pull the bobbin thread up by turning the hand wheel toward you while holding the top thread.
  2. Next, adjust the settings of your machine as follows:
    1. Select a straight stitch using the stitch selector on your sewing machine. If you’re using a mechanical machine, this is most likely a dial with icons of different stitch types printed on it. If you’re using a computerized machine, you may need to choose the straight stitch by using the buttons and touch screen. 
    2. Set the stitch length to 2.5, and the tension to 4 or 5. These are the default settings on most machines and they’re a good place to start.
    3. Select the left needle position, which will tell your machine to push your needle 2 mm to the left. This will give you an even ⅜” / 1 cm seam allowance when you align the edge of your fabric with the right outer edge of the presser foot.
  3. Place the two layers of fabric you want to join together so that their edges are perfectly aligned with each other. You can pin them together using sewing pins if you like. 
  4. Place the two layers under the presser foot while the foot is in its raised position. There are two things you need to watch when you’re placing the fabric:
    1. The fabric should be placed enough towards the back so that the needle hole is entirely covered by fabric.
    2. The right edge of the fabric should be aligned with the right edge of your presser foot. NOTE: If you want to use a different seam allowance than ⅜” / 1 cm, align the right edge of the fabric with the relevant seam allowance guide on the needle plate and use a center needle position.
  5. Lower the presser foot by using the presser foot lifter.
  6. Lower the needle by turning the hand wheel towards yourself or using the needle up / down button on your machine.
  7. Put your left hand near the left of the needle, flat on the fabric. Place your right hand towards the front of the needle. Don’t pull or tug the fabric as you sew, the fabric should smoothly feed through your machine without you having to pull or push it. Use your hands to gently guide the fabric, keep the layers aligned together, and follow your seam allowance guide (in this case it’s the right edge of your presser foot).
  8. Place your foot on the pedal, and slowly push down. When the machine sews 2-3 stitches, pause and press the backstitch / reverse button. Sew another 2-3 stitches while pressing the button, and pause again. Let the button go. You have now backstitched, which will prevent your stitches from coming undone. You will need to backstitch at the beginning and end of each seam.
  9. Slowly push down on the pedal to resume sewing. Try to go slowly, and keep your eyes on the edge of the fabric. It should always be aligned with the edge of the foot. Don’t watch the needle go up and down. Feel free to pause if you need to readjust your fabric, your hand position, or anything else to keep your sewing straight.
  10. When you reach the end of your seam, backstitch again by pressing on the reverse button for 2-3 stitches.
  11. Raise the presser foot by using the presser foot lifter.
  12. Take the fabric out of the machine and trim the threads off by using the thread cutter on the side of your machine or some thread snips / scissors.


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This article was written by Nisan Aktürk and edited by Sara Maker.

Nisan Aktürk (author)
Nisan started her sewing journey in December 2019 and already has a fully handmade wardrobe. She’s made 50+ trousers, 20+ buttoned shirts, and a wide array of coats, jackets, t-shirts, and jeans. She’s currently studying for her Sociology Master’s degree and is writing a thesis about sewing. So she spends a lot of her time either sewing or thinking/writing about sewing! Read more…