Seam allowance is the distance between the cut edge of your fabric and your line of stitching. It is included in the pattern pieces to give you fabric to sew into — without it, you would sew right at the cut edge and the seam would fall apart immediately. Understanding and maintaining consistent seam allowance is one of the most important beginner skills. Read our guide on how to use a sewing pattern alongside this article.
Why This Pattern Is Perfect for Beginners
- Consistent seam allowance produces garments that fit exactly as the pattern intends
- Inconsistent allowance is one of the most common causes of poor garment fit
- Knowing whether seam allowance is included in a pattern is essential before cutting
- The standard garment seam allowance (1.5cm) should become automatic with practice
- Different countries and pattern brands use different standard seam allowances
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Standard Amounts by Region
UK/Europe: 1.5cm (5/8 inch) standard
USA: 5/8 inch (1.5cm) standard
Japan: 1cm common
Vintage patterns: often 1.5–2.5cm
Included vs Not Included
Some patterns include seam allowance in the printed pieces. Others print the stitching line and require you to add seam allowance when cutting. Always check the pattern instructions — this is stated clearly in quality patterns.
Where to Use Larger Allowance
Curved seams (crotch, armhole) benefit from 1.5cm. Straight seams work well at 1cm–1.5cm. Always use the amount stated in your specific pattern.
How to Sew Consistently
Use the guide lines engraved on your machine's throat plate. The 1.5cm guide line is present on virtually all machines. Keep the fabric edge aligned with this line as you sew.
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All SewSimple patterns state seam allowance clearly and include illustrated instructions — instant PDF download, sizes XS to 5XL.
✨ Browse All PatternsBest Fabrics
| Fabric | Result | Ease |
|---|---|---|
| 1.5cm / 5/8 inch | Standard for most garment patterns | ⭐⭐⭐⭐⭐ |
| 1cm | Common in Japanese patterns and simple garments | ⭐⭐⭐⭐ |
| 2cm | Used for complex curved seams by some designers | ⭐⭐⭐ |
| 6mm / 1/4 inch | Used in quilting — not standard for garments | ⭐⭐ |
Step-by-Step Sewing Guide
Always check if seam allowance is included
Before cutting any fabric, check whether your pattern includes seam allowance in the printed pieces or whether you need to add it manually. This information is stated in the pattern instructions or on the pattern tissue itself.
Use the throat plate guide
The lines on your sewing machine's throat plate show standard seam allowances. The 1.5cm line is marked on virtually all machines. Keep your fabric edge aligned with the appropriate line as you sew — do not try to follow a drawn line on the fabric.
Sew at consistent speed
Maintaining consistent seam allowance requires controlling your sewing speed. Sewing slowly allows you to keep the fabric edge aligned with the guide line accurately — speed up only once keeping consistent allowance feels natural.
Mark critical areas
For very curved seams, draw the seam line directly on the fabric using tailor's chalk and sew along the marked line rather than using the guide line. This is most useful for crotch curves and armhole curves.
Check seam allowance after trimming
Many patterns ask you to trim seam allowances in curved areas to reduce bulk. After trimming, the remaining allowance should be consistent — check with a ruler if in doubt.
Frequently Asked Questions
What is seam allowance in sewing?
Seam allowance is the extra fabric between the cut edge of your fabric and the line of stitching. It provides fabric to sew into when joining two pieces together. Standard garment seam allowance is 1.5cm (5/8 inch) in most UK and US patterns.
Is seam allowance included in sewing patterns?
It depends on the pattern. Most commercial PDF patterns include seam allowance in the printed pattern pieces — the cut line is the outer edge of the pieces. Some patterns print only the stitching line and require you to add seam allowance when cutting. Always check before cutting.
Why does seam allowance matter?
Inconsistent seam allowance directly affects the fit of the finished garment. If you sew at 2cm instead of 1.5cm throughout, each seam uses 5mm more fabric — multiplied by many seams across a garment, this creates a noticeably smaller finished garment than the pattern intended.
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