Beginner · 15 minutes per seam · 7 steps
How to sew a French seam
A French seam encloses the raw edges inside the seam itself, so the inside of the garment looks as finished as the outside. It needs no overlocker — just two straight seams and a press in between — which makes it the best-value technique in sewing.
Why it's worth learning
French seams are how sheer and lightweight garments are finished in ready-to-wear. They also stop linen and voile fraying in the wash, which is where most homemade garments start to fail.
What you'll need
- Iron
- Trimming scissors or a rotary cutter
- Nothing else
Fabric notes
- Perfect for voile, lawn, silk, chiffon and light linen.
- Not suitable for thick fabric — the enclosed allowance becomes a stiff ridge.
- Works best on straight or gently curved seams; avoid on tight curves like armholes in heavy fabric.
The steps, in order
- 01
Start with wrong sides together
This is the part that feels backwards. Place the two pieces wrong sides together, so the first seam sits on the outside of the garment.
- 02
Sew the first pass narrow
Stitch about 1 cm from the raw edge if your total seam allowance is 1.5 cm. Consistency matters more than the exact number.
- 03
Trim the allowance right back
Trim to 3 mm. Anything longer will poke out of the finished seam as whiskers.
- 04
Press the seam flat, then fold and press again
Press the seam to one side, then fold the fabric right sides together along the seam line and press so the trimmed edge sits neatly inside the fold.
- 05
Sew the second pass
Stitch about 6 mm from the folded edge, enclosing the trimmed allowance completely inside.
- 06
Press the finished seam to one side
The finished seam behaves like a single flat-felled ridge — press it towards the back on side seams so it sits comfortably.
- 07
Check no whiskers show
Hold the seam up to the light. If threads escape the fold, your second pass was too narrow — restitch a millimetre further out.
Mistakes worth avoiding
Starting right sides together
You end up with the raw edges on the outside of the garment. If it happens, unpick the first pass — it is quicker than it sounds.
Not trimming close enough
Loose threads work their way out of the seam and the finish looks messy from the right side.
Using a French seam on thick fabric
Four layers of twill inside a seam creates a hard ridge that shows through the garment.
Practise it on a project
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