• No Products in the Cart

How To True A Sloper

Over the past two weeks, I have posted tutorials on how to draft the basic bodice sloper (click here to see the tutorial for front bodice and click here to see the tutorial for back bodice). Before I move onto the sleeve draft, the front and back bodices must be trued.

For all newbies to the subject of slopers and blocks, I’ll give a quick definition of truing. Truing patterns is the process of checking and correcting seam lines, shapes, and measurements on a pattern. It’s the process of making sure the seams of two adjoining pattern pieces equal, making sure both legs of a dart are the same length, and making sure that shapes are smooth as they continue through different seams. 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 any seams that aren’t meant to be will cause puckering.

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

So let’s get to it…

Darts and right angles:

To true darts, fold dart along the center of dart intake and match stitching lines starting from dart point. With intake folded towards either CF/CB or SS, check if dart legs are the same lengths. If they are not, increase or decrease dart leg accordingly and redraw seamline that dart legs connect with to create a smooth transition as the seam continues through the dart.

When a seam meets another seam, an example being when SS meets waist seam, almost always the seams should be at right angles to each other. The exceptions are necklines and armholes at shoulder seam, which I will explain just below. If these points are not at right angles to each other, when the seam is sewn, the seam will be point up or down. With that said, check to make sure all points except AH and neck at shoulder seam are a right angle. It is okay if you have to curve the seam right before this point.


To true the neckline, butt the front and back pattern pieces together at neck/shoulder seam. Using a curved ruler, draw a smooth curve from front neck to back neck (or vice versa). This point does not have to be at a right angle; just use common sense, the neck is a circle, how could this point be at a right angle?


To true the armhole, butt the front and back pattern pieces together at AH/shoulder seam. Using a curved ruler, draw a smooth curve from front armhole to back armhole (or vice versa). According to textbooks, this point “should” be at a right angle but in my opinion, it doesn’t have to be. Every person’s body angles and curves differently and your front or back armhole may be too scooped for this point to be at a right angle. Try your hardest to make this point a right angle as it is “better” but if you can’t, then don’t sweat it. A smooth transition is more important.


  1. Reply


    Awesome! Seeing you “right angle” illustrations makes so much sense!! No more trimming off the edges post construction…

    • Reply


      Glad it helped. If the pattern is correct, you won’t have to make any adjustments during sewing.

  2. Reply

    Rochelle New

    Ooooh thank you for sharing this!! Definitely book marking it for future reference 🙂

    • Reply


      Welcome 🙂

  3. Reply


    I love this tute! I am just about to start working on my bodice sloper. It has been a long time since I have made one and I need all the help I can get! Your illustrations are very good!

    • Reply


      Glad it helps and feel free to email me if you have any questions.

  4. Reply


    🙂 I love your drafting tutorials! Very easy to understand and great illustrations!

    • Reply


      why thank you 🙂

  5. Reply


    Ohhhh Madalynne! You changed the font!!!! Thank you, my eyes are so grateful! You are a great teacher!

    • Reply


      Yes I did! My readers come first and I’m glad you liked my post. There will definitely be more to come so stayed tuned.

  6. Reply


    A question for you… Is the process of truing supposed to happen before or after adding seam allowance? Or does it not matter? Also, what do you do if you recheck all measurements and two seams still are not perfectly equal? My shoulder seams still are not the same size even though I double checked! Thanks in advance!

    • Reply


      Trying can be done before or after adding seam allowances; the same principles apply (seam lengths should match and points should be at right angles).

      As for shoulder seam length, reduce or increase the length to match the measurement you took when you measured yourself. When drawing the shoulder seam line on the back bodice pattern, the line was “suppose” to be placed on the vertical guideline but the directions stated that it was okay to reduce or lengthen the line if it did not meet or extended past the guideline. The most important thing is that the back shoulder seam measurement equaled the front.

    • Reply


      Excuse me, I meant truing (damn autocorrect)

    • Reply


      Thanks so much for you quick reply!!

  7. Reply


    Wow! That’s so helpful! Thanks!

  8. Reply

    Sylvia Ryals

    Thanks for this! I never read anything about sewing that was too geeky. I’m thrilled to be here.

    • Reply


      And I’m thrilled to be writing here

  9. Reply


    Thanks for the tutorial. I’m going to bookmark it and try it soon. 

    So, truing a pattern is the same as walking a pattern??

    • Reply


      I’m glad you found this tutorial useful!

      Truing a pattern has many steps (i.e. making sure seam lengths equal on two pattern pieces that will later be sewn together)and walking the pattern is one of those steps.

  10. Reply


    I have tried to read many tutorials to make a bodice.. yours , i must say, is the most understandable .. Will try this soon …. Following you !

  11. Reply


    Your tutorials have been, by far, the most clear and concise of the many I have read! Thank you! I am a beginner and was curious if you could give me some pointers on truing the ss? I am very tall and bigger busted. My back bodice is about 2.5″ shorter than my front and my ss do not match up. Do I simply extend my back bodice length or is there a better alternative?

  12. Reply


    I have a question, I have been thinking about drafting my own patterns for a while and have read a lot my question is when it comes to trueing side seams do they need to be the same angle? or does it not matter as long as they are the same length? I am looking forward to finally drafting something that will fit 🙂

Leave a Reply