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How to Use a French Curve, Video Tutorial!

Learning how to use a French curve in your pattern drafting is important.

So important, that I would wager to say that besides my straight edge grided ruler and mechanical pencil, I would honestly flip my sh*t if my French curve went missing. Ever since I learned about it at university, its super high on my list for top sewing tools; there is not a single project that my French curve is not integral to success.

The types of French curves on the market are numerous.

If you’re searching Amazon, I can definitely see how they might be intimidating to even think about!

The two in their listings that I would recommend are:

  • Fairgate Vary Form Curve
    • Pros: This is essentially the one I use (haha!), sturdy, can use it with my rotary blade
    • Cons: Not transparent
  • Dritz Styling Design Ruler
    • Pros: Love the gridded section, love the straight edge component, transparent
    • Cons: Plastic may snap or be ruined by cutting implements, not a dual sided curve, looks kind of flimsy for long term use

How to use a French Curve | Vintage on Tap

With so many French curves out in the market, you can use most of them in your pattern drafting. When choosing one, please just consider the following questions:

  • What are you primarily going to use it for? If for strictly pattern drafting, you’d be ok with a plastic ruler, but if you want to also be able to cut with it, stick to a metal ruler.
  • How are you planning on storing it? If hanging, make sure it has a hole in the body to hang from.
  • Is this going to be your single French curve? If so, look for a long French curve with a sharper curve at the head that can serve double duty. If you’re able to afford and have space for multiple tools, you can purchase sharper curved pieces separately and instead aim for a more traditional French curve with more gentle, natural curves.

The length of this sewing tool is super important.

Please, aim for a larger French curve that will be adequate for the length between your bust line to hip line– you may have to use this curve to blend that distance.

How to use a French Curve, blending curves in armhole | Vintage on Tap

How to Use a French Curve Tip #1: Blending jagged edges, like armholes after a full bust adjustment.

I discuss this particular tip at the 30 second timestamp.

The first consideration for this step is that you’re essentially looking for the median of the jagged edge: a line that blends as many of the points together into a smooth, curve that would feel natural against the body.

  1. Identify the areas that need to be blended and decide what type of curve it needs– convex, concave, S-shape, etc.
  2. Identify which part of the ruler will hit the right median between the points.
  3. Move the ruler around in order to capture different parts of the curve as needed. For example, if you’re working on an armscythe you might need one portion of the french curve versus if you’re blending the waist of a dress, you might need to reference 4+ edges of the ruler!

The main take away of this step, is that when you’re learning how to use a French curve, you can really make that new line do whatever you want it to do. 

Even a change in a curve of 1/4in makes a difference. If an armhole is too tight, you can change that curve as needed. If a pencil skirt is too straight, you can give it a little more va-va-voom.

Experiment with the different parts of the ruler for the best curve for the part of the garment you’re working on, but don’t forget to walk your pattern seams after doing this step, just to make sure everything lines up!

How to use a French Curve, blending pattern pieces | Vintage on Tap

How to Use a French Curve Tip #2: Blending between pattern pieces.

In my example at timestamp 1:45, I blend between the front and back pieces that aren’t matching at the side seam.

This will apply in so many different situations:

  • Blending the shoulder seams
  • Blending a bodice to a skirt
  • Blending a sleeve head
  • Blending skirt pieces to one another

The concept is pretty simple, though! If you’re walking a seam, and see that no matter what you do, your pattern pieces are not walking properly (bodice is too long compared to the back, etc.)– identify which pattern piece needs to be blended to its corresponding seam.

In practice, the steps are straight forward:

  1. Walk pattern pieces and calculate how much more needs to be added or subtracted from the “off” piece
  2. Walk pattern until the relevant seam is sitting as it will ultimately be finished (for example, if you’re working on a princess seam, walk the pattern from the top edge, down the curve, to the waist seam.)
  3. Complete steps as outlined in the video, using the French curve to redraft the seam into a smooth curve
  4. Rewalk the seam to confirm that the new seam is meeting correctly (in the above example, rewalk the seam from both the top edge AND the bottom edge of the princess seam, to make sure BOTH seam ends match up and are smooth)

How to use a French Curve, blending pattern pieces | Vintage on Tap

Completing the above process will make a brand new cut line, so be sure to only add on the appropriate amount for the seams to match. 

If you’re making a bodice for a dress, doing this step on the side seam means that you’ll have to rewalk the bodice pieces to the skirt to make sure THOSE seams match properly.

Ultimately, this is where the “drafting” in “pattern drafting” is at its full, 100% effect. You are essentially using your French ruler to mold a pattern to your body and make sure a piece of paper is translating your natural curves. Its a combination of sewing and geometry, down to the 1/4 inch.

How to Use a French Curve on Darts | Vintage on Tap

How to Use a French Curve Tip #2: Trueing a dart.

Or “truing” a dart- same thing. This step is covered at 3:56 in the video.

Essentially in this step, you’re making sure that any changes to a dart are accommodated for by making sure there is enough fabric at the bottom of the dart to fit within the seam allowance.

While this might be tricky to conceptualize, if you think back on a dart you may have had to a change on- whether its a full bust adjustment, a small bust adjustment, or even just a movement of the dart, you need to make sure that when the dart is closed, that the dart seam allowance fits neatly within the final seamline.

To get this step done, complete the following steps:

  1. Close the dart in the direction of where the dart will be pressed
  2. Identify the seam that needs to be blended
  3. Draw the new blended line using the appropriate section of the French curve. You can also use a tracing wheel for this step. Please no more than 2- max 3- passes of the tracing wheel (too many passes and the line gets “blurry” to follow)
  4. Open up the dart and complete the new dart redraw. If you used a tracing wheel, use the French curve to connect the dots of the tracing.

Please note- the above steps are for MOST darts, whether a side seam dart, a waist dart, skirt dart, whatever. At the very least, close the dart and make sure you have a smooth seamline just to confirm that your dart will sit properly when you move onto the fabric.

How to Use a French Curve on Darts | Vintage on Tap

Learning how to use a french curve can really elevate your sewing experience like crazy.

For such a simple and relatively cheap tool, it can make for better drafting overall and for better understanding of how pieces fit together.

As I cover in my Walking a Pattern video, a 1/4in here and there can add up into garments that don’t fit. By using a combination of walking seams and French curve, you can remove some of those obstacles that can make it difficult to fit clothing to the body.


I hope you found the tutorial useful!

As I said in the video, I receive lots of questions about this tool because I use it so extensively in my pattern drafting tutorials. The playlist for pattern drafting tutorials has grown like crazy at this point- and I think at this point the French curve has made in appearance in at least 50% of them!

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How to use a French Curve, tutorial | Vintage on Tap


Have you learned how to use a French curve before? Are there any other ways that you use this tool? If you haven’t used one before, why not? How can this sewing tool help your pattern drafting?


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Vintage on Tap started in 2013

Since then, it has become not only a photo blog, but also a popular YouTube channel and Instagram Feed.

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