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When it comes to sewing, a seam allowance refers to the additional fabric added to all sides of a pattern piece that will be joined together during construction. The purpose of a seam allowance is to provide sufficient room for stitching, prevent fraying, and allow for alterations if necessary. In this section, we will explore the concept of a seam allowance and its significance in sewing projects. We will define what a seam allowance is and discuss why it is an essential aspect of garment construction.


Key Takeaways:

  • A seam allowance is the extra fabric added to all sides of a pattern piece for stitching purposes.
  • A seam allowance prevents fraying and provides room for alterations.
  • Understanding and accurately measuring seam allowances is crucial for successful sewing projects.


Understanding Seam Allowance Measurements

When it comes to sewing projects, accurate seam allowance measurements are essential for achieving precise results. Seam allowance is the extra fabric between the stitching line and the edge of the fabric, which ensures that seams do not unravel or fray over time. There are various methods for measuring seam allowances, each with its advantages and disadvantages. The most common way is to use a seam gauge, which is a small metal ruler with a sliding marker.

When measuring seam allowances, it is important to ensure that the seam allowance is consistent and even throughout the sewing project. This can be achieved by using a seam guide or painter’s tape to mark the desired measurement on the sewing machine. The standard seam allowance measurements used in sewing patterns vary depending on the project and fabric type. For example, a seam allowance of 5/8 inch is commonly used in garment construction, while a quarter-inch seam allowance is ideal for quilting projects.

To achieve accurate seam allowances, it is essential to use the appropriate measuring tools and to take your time when measuring and marking the fabric. A little extra effort at this stage can save you a lot of time and frustration in the long run.


Importance of Seam Allowance in Sewing

Seam allowance plays a vital role in creating a well-constructed garment. It refers to the extra fabric beyond the stitching line, which allows for adjustments and modifications during the sewing process. The seam allowance is essential for the following reasons:

  1. Room for alterations: When creating a garment, it’s essential to have a seam allowance that allows for customizations, such as letting out or taking in seams. Without a seam allowance, modifying the garment becomes difficult.
  2. Preventing fraying: A seam allowance prevents the fabric from unraveling and fraying at the edges, making the garment more durable and long-lasting.
  3. Enhancing the durability of the garment: By providing extra fabric and reinforcing the stitching, the seam allowance helps to keep the garment’s shape and structure intact.

Therefore, including seam allowances in your sewing projects is essential to achieving a professional-looking garment that fits well and withstands everyday wear and tear.


Different Types of Seam Allowances

Seam allowances come in various types and sizes, and choosing the right one can make a significant difference in the outcome of a project. The most common seam allowance widths are ⅝ inch, ½ inch, and ¼ inch.

Standard Seam Allowance: The standard seam allowance is ⅝ inch, and it is used in most commercial patterns. This width provides ample space for adjustments and alterations once the garment is constructed.

Narrow Seam Allowance: A narrow seam allowance, typically ¼ inch, is best used in fine fabrics or intricate designs where bulk is a concern. This type of seam allowance is also ideal for curved seams that require close clipping or grading.

Wide Seam Allowance: A wide seam allowance, such as 1 inch, is commonly used in home decor projects or when extra fabric is needed for a particular technique, such as French seams.

Flat-Felled Seam Allowance: A flat-felled seam allowance is a type of seam where the raw edges are enclosed within the seam. It is used in jeans, shirts, and other heavy-duty clothing items.

Double-Stitched Seam Allowance:

A double-stitched seam allowance is typically used in stretchy fabrics. This type of seam is made by sewing two rows of stitching parallel to the seamline and then trimming the excess fabric to about ⅛ inch. The result is a narrow but strong seam that has a bit of stretch. Choosing the right seam allowance type and width is important for achieving the desired result in your project. Be sure to consult the pattern instructions or research the appropriate seam allowance for your specific fabric and project type.


Seam Allowance Techniques for Different Projects

Seam allowances are a crucial aspect of garment construction and quilting. The size of the seam allowance can vary depending on the project, fabric, and sewing technique. Here, we will explore the specific seam allowance techniques required for different types of sewing projects.

Seam Allowance for Garments

When sewing garments, it is essential to follow the seam allowance guidelines provided in the pattern instructions. The standard seam allowance for most garments is 5/8 inch (1.6cm). However, some patterns may call for a larger or smaller seam allowance. It is essential to measure and cut the seam allowance accurately to ensure a precise fit of the garment. For curved seams, it is recommended to use a smaller seam allowance to prevent bunching and puckering. You can also clip the seam allowance at regular intervals to allow it to lie flat.

When sewing with delicate or lightweight fabrics, it is recommended to use a narrow seam allowance to reduce bulk. On the other hand, for heavy fabrics, a wider seam allowance may be necessary to prevent the seam from unraveling.

Seam Allowance for Quilting

When quilting, the standard seam allowance is ¼ inch (0.6cm). This size provides enough fabric for a strong seam while limiting bulk in the quilt’s layers. When joining quilt blocks together, it is recommended to press the seam allowance to one side to reduce bulk and create a smooth finish. It is also crucial to ensure that the seam allowance is consistent throughout the entire quilt to prevent any distortion in the final product.

When sewing long strips of fabric together for a quilt, it is essential to use a consistent seam allowance to ensure the strips fit together correctly. It is recommended to use a walking foot attachment on your sewing machine to help the fabric move smoothly and prevent any stretching or distortion of the seams. By following these seam allowance techniques for different projects, you can achieve professional-looking results in your sewing and quilting endeavors.


Seam Allowance Adjustments and Modifications

Adjusting and modifying seam allowances is a common practice in sewing to accommodate individual preferences and specific requirements. Here are some techniques to help you adjust and modify seam allowances:

  • Enlarging seam allowances: If you require a larger seam allowance, simply draw a new stitching line alongside the original seam line, trimming away the excess fabric. This is particularly useful when making alterations to a garment.
  • Reducing seam allowances: To reduce seam allowances, carefully trim away the excess fabric without cutting into the stitching line. This technique is commonly used in curved seams to reduce bulk and achieve a smoother finish.
  • Combining seam allowances: For some sewing techniques, such as flat-felled seams or French seams, it may be necessary to combine two or more seam allowances. This creates a stronger and more durable seam.

It is important to note that adjusting seam allowances can affect the fit and overall look of a garment, so be sure to make any changes gradually and with caution. Additionally, it is always a good practice to test any modifications on a sample piece of fabric before applying them to your project.


Seam Allowance Best Practices

When it comes to working with seam allowances in sewing, there are some best practices you should follow to achieve professional-looking results. Here are some tips and techniques to keep in mind:

  • Measure twice, cut once: Accurately measuring your seam allowance before cutting your fabric is key to ensuring a proper fit and avoiding costly mistakes.
  • Press your seams: To achieve clean and polished-looking seams, always press them flat after stitching. This helps to set the stitches and minimize bulk.
  • Use the right finishing technique: Depending on the fabric and the project, different seam finishing techniques may be appropriate. Some common finishing techniques include serging, zigzag stitching, and French seams.
  • Clip corners and curves: When sewing shapes with corners or curves, clipping the seam allowance can help the fabric lay flat and prevent bunching or puckering.
  • Grade your seams: For bulky fabrics or seams, grading the seam allowance by trimming it in layers can help reduce bulk and create a smoother finish.
  • Handle bulk carefully: When sewing with thicker fabrics or multiple layers, take care to ease the bulk of the seam allowance to prevent distortion or puckering.

By following these best practices, you can achieve professional-looking seams and ensure that your sewing projects are both functional and aesthetically pleasing.



Seam allowances are a crucial aspect of successful sewing projects. They provide room for alterations, prevent fraying, and enhance the durability of the garment. It is essential to accurately measure and use the appropriate type of seam allowance for the fabric, garment type, and sewing technique. When working with seam allowances, it is important to follow best practices, such as proper pressing, finishing techniques, and handling bulk. These techniques ensure clean and professional-looking seams. By understanding and applying the guidelines and techniques discussed in this article, you can achieve precise and professional results in your sewing endeavors. Remember to always measure twice and cut once to avoid any mistakes.

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*Please note: The "What is a seam allowance?" post is for general informational purposes only. Please consult with a local alteration tailor shop near you for specific advice or if you are located in Toronto or the Greater Toronto Area simply contact us.