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Knit Basics: Know Before You Sew - Fitting Knit Pants

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Knit Basics:  Know Before You Sew - Fitting Knit Pants

Knit pants have gained popularity over the years.  For good reason, they are not only comfortable but stylish.  You can have everything from leggings, casual athleisure, classic pants, jeans, full evening pants and everything in between.  Depending upon the desired ease, these techniques will work fabulously for stretch woven with no or minimal desired ease. 

When it comes to fabric, I would recommend a Ponte double knit or Scuba knit.  The weight of the fabric would vary depending upon design.   For most knit pants I would recommend a more substantial weight (min. 300 GSM).   Some Ponte knit can be as beefy as 480 GSM which would be fabulous for a very structured pant with little to no drape.   For a full evening pant, a lighter weight Ponte (230 GSM) would hang away from the body but still provide the drape suitable for the design. 

Structured Knit Pant    Full Knit Pant                                                          V1867 - structured pant                                   B6851 - wide drapey pant

One important factor when selecting fabric for a knit pant is to ensure good stretch recovery so you don’t get bagging in the knees or derriere.   For more information on fabric weight or suitability check out Part 1 of this series – Selecting the Right Fabric.   

The amount of ease you prefer, and your fabric selection, will have an impact on the pattern size you choose.   To start, measure your hips at the fullest part above your crotch.  If you tend to be fuller in the thighs (below your crotch), don’t measure there otherwise you won’t get a good fit in the crotch.   The inseams or side seams can always be let out to accommodate this fullness.  

Measuring HipsMeasure level to the floor 


Now take into consideration your personal preference regarding ease.  Do you want them to fit like a woven pant with wearing ease, have no ease like a skinny pant, or negative ease like a legging?

  Example of wearing ease  Example of No ease               

Wearing ease (B6845)                                      No ease (M6173) 


Example of Negative Ease             Negative ease (M6173)


By the nature of a knit, ease is built in due to the weave and addition of spandex.  However, every knit is different so it’s difficult to provide hard and fast rules that cover all types of knits (and stretch wovens).   I find most tend to overfit making their knit pants too big.   A blended approach of tissue and fabric fitting will help to address this concern.  In my opinion the fabric fitting stage replaces the need for a muslin.    Helen Bartley has perfected this method in her book Fit and Sew Custom Jeans.   I have used a similar approach to fitting knit pants, so it is well worth exploring.  

The next step is to incorporate the stretch of the fabric in determining your size.   Helen calls this the “wrap test”.  

Warp test for fabric

Wrap test


Fold your fabric on the crosswise grain (greatest stretch), wrap around your body snuggly based on your degree of comfort.  This measurement would be your preferred finished garment measurement (FGM) in your fabric.  You would then choose a pattern size close to this FGM.

Let’s work through an example to enhance understanding.  Say we wanted to make a skinny pant (M6173) and not sure what pattern size to work with.   In the example below, our hip measurement is 40.5".  We did the wrap test with our knit fabric and determine that 38" would be a comfortable FGM.

Measurement Chart to determine size

chart from Fit and Sew Custom Jeans


The pattern size for our hip measurement would be Large (16-18) and would have an FGM of 42.5".   That would allow for 2" of wearing ease (42.5" – 40.5").   Since we determined that a preferred FGM is 38", the Large size would definitely be too large.  Looking at the chart below, based on our preferred FGM of 38", we would select a size Medium (12-14). 

 Szie chart


Tissue fitting knit pants can be challenging if you are working with zero or negative ease.   This is where a hybrid approach works well.  You can check crotch depth and shape, leg width and overall length in tissue before going to fabric.   You will notice in the picture below that the side seams don’t meet.  This is because my preferred FGM is less than my actual hip measurement.   

Tissue fitting for knit pants


I have been able to determine some guidelines to know if you have enough circumference while tissue fitting.  If you are unsure, having 1" side seams also provide some assurance.  

Preferred Ease

Gap Amount at Side Seam

Wearing Ease

Tissue meets at cut edges

No Ease

1.5" gap at side seam

Negative Ease

3.0" gap at side seam


Helen also has a great method in her Jeans book where she recommends adding tissue to the side seams to facilitate tissue fitting which is removed before cutting fabric.   I recently attended the Jeans workshop with Helen and tried this technique with my stretch denim jeans and it worked great.  Bravo Helen for figuring this one out!  Sometimes the obvious isn’t that obvious to us. 😊

There is one depth issue that I know I need to address with the tissue before I fabric fit.  I have a very flat low back which always results in too much fabric under by derriere.   If you pull up the fabric in the back and these wrinkles disappear you know you need this adjustment as well.  The trick is the amount which is dependent upon your fabric.  Due to the amount of stretch in my Ponte I decided to do a ¾" tuck in tissue and fine-tune in fabric.

Tissue adjustment to remove depth


Since I had a 2-piece back, I needed to ensure that the tuck ran right thru the back and side back.  I knew this would make the back crotch too short, so I lowered the crotch equal to the amount of the tuck and straightened the side seam.    

Tissue - lower crotch curve


After completing as much fitting in tissue as possible, I will complete the rest in fabric – the hybrid approach.

Some might ask, why not create a muslin?  Well yes you can, but to properly assess the adjustments needed, it is important to create the muslin in comparable fabric (i.e. same Ponte knit).   If you are going to go to that effort and cost, I prefer to have a garment at the end of the process that I can wear.   It may take a pair or two to perfect the fit but you will have a great fitting pant on the first try.  

The remaining adjustments are more easily made in fabric.   I want to share a couple of common adjustments that I need.   I sometimes get a bubble in the front crotch meaning I need a straighter front crotch seam.  You take away the width (excess fabric) by straightening the front crotch seam.  Doesn’t seem intuitive but it works!

Example of crotch bubble  Straighten front crotch

                  Crotch Bubble                                                  Deepen (straighten) front crotch

Since I am flat and low in the back, I often get puddles (excess fabric) under my derriere.   Even though I did remove length in the tissue I still need to fine-tune my back crotch in fabric.  You can see by the picture below that I don’t have enough seat room.  This is causing the drag lines (puddles).  I also have extended calves which is causing some pulling as well. 

Puddle in back of pant   

Puddles in back                                        Lower front crotch

Knit pants are so comfy and stylish that I would encourage you to give it a try.  It can be a bit of trial and error, but you will begin to see the cause and effect of different fabrics.   Getting started in the right size will go a long way to having that great fitting pant.  I must admit I am still learning and fine-tuning my fit with every pair and change in fabric.

For additional information on fitting and sewing pants, I would highly recommend the following books:

Pants for Real People   Fit ans Sew Custom Jeans


Follow along the entire Knit Basics:  Know Before You Sew series:

Part 1:  Selecting the Right Fabric 

Part 2:  Fitting Knit Tops

Part 4:  Layout, cutting and marking (coming soon)








1 Response

Helen Bartley
Helen Bartley

February 22, 2023

Janice! Wow! This really makes me want to make some activewear now. I love the specific fabric references. Weight, recovery, drape-all so important. A very nice, thorough explanation for great results with any pant with negative ease. Thank you for the book references, too.

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