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Pattern Making: How To True A Bodice Sloper: Update


You have drafted the front and the back bodice sloper and now what? Now, it’s time to true.

Truing is the process of checking and correcting measurements, seam lines, and pattern shapes on a pattern. It’s ensuring the lengths of two adjoining pattern pieces equal and the lengths of right and left dart legs equal. Truing is also making sure that seams and shapes transition smoothly as they continue through seam lines. If truing is not done, then when it is time to sew, one seam or dart leg may be longer than the other and stretching or easing it to fit would cause puckering.

Although this tutorial covers how to true a bodice sloper or block, it can be applied to any pattern. Essentially, every pattern that is altered should be trued.

So let’s get to it…

{LENGTHS} Measure front and back pattern pieces at side seam and shoulder seam and ensure the lengths equal (be sure to eliminate dart intake on back shoulder dart)

{DARTS} Measure the lengths of the right and left dart legs. Are they equal? If not, reduce or increase accordingly until they are. Next, fold dart along the center of dart intake, matching stitching lines from seam to dart point and with intake folded towards CF/CB (see diagram 3). Does the dart intake “point out” as in diagram? If so, recut/redraw seam line so that it transitions smoothly throughout the entire seam and that nothing “sticks out.”

{RIGHT ANGLES} With the exception of armholes and necklines at shoulder seam, all seams must meet/intersect at a right angle. This includes the intersection of armhole and side seam, waistline and side seam, front and back necklines and CF/CB, and front and back waist lines and CF/CB. If these seams do not intersect at a right angle, the seam will “point up” or “point down” at the seam.

Butt pattern pieces together as on diagram 1 and ensure all seam lines stated above intersect at a right angle. If they do not, redraw seam lines. It is okay if you have to curve the seam before it intersects with another seam to achieve a right angle.

{NON RIGHT ANGLES} Armholes and necklines at shoulder seam are the two exceptions where the seam should not intersect at a right angle. The reason is that these seam lines are a circle (somewhat). The most important thing is that the neckline is a smooth curve from CB to CF or vice versa. The same can be said for the armhole.

Butt the front and back pattern pieces together as on diagram 2 and using a curved ruler, draw armholes and necklines so that they transition smoothly through shoulder seam.


  1. Reply


    What a great tutorial! You are bringing back so much for me that I had forgotten from pattern making class!

  2. Reply


    I can’t tell you how much I have learnt with these tutorials of yours, thank you!

  3. Reply

    Deanna Pryce

    You are a great teacher! this has been exciting and simple to follow!

  4. Reply


    hi 🙂 can you also give us a checklist for the torso, sleeve and skirt basic slopers?

    • Reply

      Maddie Flanigan

      It is on my to-do posts, but I haven’t gotten around to it yet. Stay tuned!

  5. Reply

    Geri O'Donnell

    This is exactly what I’ve been scoring the web for! Thank you 🙂

  6. Reply


    Hi Maddie – I have a question now that I am truing my sloper (novice at patterning), doe P, Q & R form an actual dart? I can see that they are not drawn on these diagrams, but I had assumed it was, and I’m confused with how it works since it actually overlaps with the armhole. Thank you!

  7. Reply


    Sewed for myself years and many sizes ago…chuckle…your tutorials have eased my worries in starting up my favorite hobby again. Thank you from the bottom of my heart.

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