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The Ultimate Guide to Seam and Hem Allowances for Drafting Your Own Sewing Patterns

In the world of sewing and pattern cutting, seam and hem allowances play a crucial role as they serve as the finishing touches to complete your self-drafted sewing patterns. It's important to handle them with care, following the guidelines below.

Seam and hem allowance guidelines
Sneak peek at the hem and seam allowance guidelines. Scroll down to see a full break down of each in more detail.

Always remember the golden rule: Seam and hem allowances are the last guests to arrive at the party! 🎉🧵 They come in after you've made all your design decisions, whether it's a single adjustment or a series of changes. Adding seam and hem allowance should be the last thing you add to your sewing pattern and you should never change them or add extra bits of design features to them.



If you're uncertain about which type of hem or seam to choose, take a look at the tables below. They'll help you make the right choice for your design and fabric.


 

Ultimate Guide to Hem and Seam Allowances

Mastering Seam Allowance Guidelines


Plain Seam (the seam most commonly used) Seam allowance required: 1cm or 3/8" Plain seams are either pressed with the raw edges open or facing toward the back of the garment.


Diagram of a plain seam

French Seam Seam allowance required: 1.5cm or 5/8" This technique is often used on lightweight fabrics that fray easily. You may use it when you desire a beautiful finish on a silk shirt.

Diagram of a french seam



Double Stitched Seam Seam allowance required: 1cm or 3/8" Good for knit fabrics to stop the fabric from rolling but can be used on woven fabrics too

Diagram of a double stitched seam

Flat-felled Seam Seam allowance required: 1.5cm or 5/8" Traditionally, this method is used on the inside leg seams of jeans.

Diagram of a flat-felled seam

Here is a flat-felled seam on a pair of jeans.

A picture of a flat-felled seam on a pair of jeans
Image of a flat-felled seam (picture sourced from Pinterest)

Bound Seam Seam allowance required: 1.5cm or 5/8" This seam is great to use on coats or jackets that don't have a lining.


Diagram of a bound seam

Here is a bound seam on the inside of a sleeveless overcoat I made.

Image of a bound seam inside a sleeveless overcoat
Image of a bound seam


Want to listen to a detailed explanation of various seam allowance guidelines? Check out my YouTube video here.




Hem Allowance Guidelines: Crafting Neat Finishes


Double Fold Hem Hem allowance required: 1.5cm or 5/8" This is the most common hem, as it hides raw edges and prevents fraying


Diagram of a double fold hem

Narrow Rolled Hem Hem allowance required: 0.6cm or 1" Great for light fabrics, especially silk, and for finishing curved edges (you can get your hands on sewing machine feet designed to assist with this process).


Diagram of a narrow rolled hem

Ignoring the cream elastic, here is an example of a narrow rolled hem I used to finish my bamboo silk top.

Image of a narrow rolled hem
Image of a narrow rolled hem

Here is our favourite tutorial by Daria Pattern Making on how to sew a narrow rolled hem/baby hem https://www.instagram.com/reel/CgCVI1ZqhTA/


If you're keen to jazz up your rolled hems then try this method below...




Blind Hem Hem allowance required: 2cm + or 1 1/2" A hem that is often used on trousers, skirts and curtains.


Diagram of a blind hem

Zigzag/ Overlocked Hem Hem allowance required: 1.5cm or 5/8" Another frequently used seam, which results in less bulk compared to a double fold, requires only a single fold due to the zigzagged raw edge.

Diagram of a Zigzag/Overlocked hem

Here I used an overlocked edge to finish the bottom of the facing inside a dress I made. If you were to do this on the bottom of the dress you could then use the overlocked hem to finish the look.

A picture of the inside of a dress showing an overlocked hem to finish the facing
Overlocked hem on facing

Knit Hem Hem allowance required: 1.5cm or 5/8" A long, narrow zigzag stitch is used with stretch fabrics to prevent thread breakage while allowing for stretching.


Diagram of a Knit hem


***Keep in mind that when working with thick fabric, larger hem allowances will be necessary*** 


Want to listen to a detailed explanation of various hem allowance guidelines? Check out my YouTube video here.



TOP seam and hem allowance TIPS to take away today...

  1. Always add hem and seam allowance last.

  2. If you ever need to make adjustments to a sewing pattern, be sure to mark the locations of the hem and seam allowances. This way, you can avoid altering them by accident. If necessary, you can always trim them off and then add the hem and seam allowance back in later.

  3. Make sure to mark any notches accurately across your seam allowance using your pattern ruler to ensure precision.

  4. Press as you go! Ironing and pressing your seams and hems as you sew will give your project a professional finish.


You can really make the seams and hems a key future on your garments to add extra flair and show off your skills. Check out our inspiration from Pinterest below to get your creative juices flowing...


A moodboard of seam and hem inspiration images taken from Pinterest
Seam and hem inspiration images taken from Pinterest
 

Download the hem and seam allowance charts inside my FREE eBook below...


Free pattern cutting eBook pages. The pages displayed are seam and hem allowance guidelines

Get more from your sewing projects and release your creative potential in pattern drafting and dressmaking!


Grab your FREE copy of my eBook, 'An Introduction to Pattern Cutting', to learn how to start creating sewing patterns for clothes you love. Learn the basic foundations of pattern drafting, discover a list of essential pattern cutting toolsyou need, learn more about pattern blocks/slopers and so much more.


Take a peek inside! ⬇️

Pages from a free pattern cutting eBook created by The Sewing Retreat

Happy sewing,

Sarah x

P.S. I'm a real person and we have a fabulous team here behind the scenes eager to help❤️. Feel free to send us a DM on Instagram or an email to hello@thesewingretreat.co.uk if you have any questions, We'd love to hear from you :)



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