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How To True A Pattern: Truing Darts, Seams And More

This article is all about truing up your newly created patterns. If you haven’t yet created a sewing pattern, you can learn how to create a block / sloper from a commercial clothing pattern or even draft a female bodice block to get started.

Truing patterns – the darts, the seams and more – is essential to make sure that the sewing pattern is as accurate as it can be.

Knowing how to true a pattern is not quite as complicated as you might think it sounds so this week I’m going to clear up any confusion you might have.

Some of the links in this article are affiliate links. This means that I may receive a fee at no extra cost to you if you purchase a recommended product.

A dart being trued up in pattern paper on a while table top

What Is Truing?

Truing is the term used in sewing and pattern making when we make sure things match up.

It could be a dart that you have moved around the bodice and you check that each dart leg is the same measurement.

Or it might be an adjusted seam line that now needs to be checked so that it matches it’s other half.

It could even be that an adjusted pattern piece now has smooth lines once modified.

‘Truing’ then is the process of making sure things match up how they are supposed to.

What Is A True Line?

A true line is a tidy line which will give us the outcome we want in our fashion creations. This image below is of an armhole being trued up during my old ‘Create Your Own Clothes‘ series.

Truing The Dart - The Creative Curator

You can see from the photo that when I closed the dart in the armhole, the two sides of armhole don’t ‘true up’. There is a step.

If we were to leave this as it is, it would end up being quite an unattractively shaped armhole.

Or if the dart were sewn in such a way that the armhole edges were meeting, we would have a ‘gather’ of some sort on the one side of the dart which wasn’t part of the design!

In the photo below, you can see that the difference has been corrected. This pattern piece has now been ‘trued up’.

Truing Up A Dart - The Creative Curator

This is how you would true up a dart. But you will also need to true up other elements of a pattern if you are adjusting a pattern’s size or design.

2 Ways to Adjust A Pattern’s Size

One thing to be aware of. There are different ways to adjust your sewing pattern’s size.

  1. You can grade it properly – which means to make it bigger or smaller all over, using set measurements for each size graded.
  2. Or, you can make it up yourself.

As an example, you may have a pair of trousers that are too long in the leg for you. You plan to modify the pattern to shorten the length and do this by taking out an inch in the front leg pattern and again on the back leg pattern. When you do this, you need to ensure two things.

  • The grain line is still a straight line when the process is complete.
  • The pattern pieces have been trued to make sure that there are no issues when it comes to sewing the trousers together.

Checking Other Pattern Elements

There are several ways to check other pattern elements that need truing up.

  1. Walk pattern pieces
  2. Measure pattern pieces

Walking Patterns

To check that pattern elements are correct, we can ‘walk’ them. If we were checking the inside leg of a pair of pants / trousers we would lie the back inside leg on the work table in front of us, and pop a weight of some sort on top, so that the pattern piece doesn’t shift.

Then we take the front leg, and pop the crotch point of the front leg to meet with the crotch point of the back leg. They should lie flat on top of each other.

Very carefully and slowly – this isn’t a rush job – we walk the front pattern along the back pattern, making sure that we are matching the seam lines, NOT the seam allowance edge!

There is often ease added to certain areas of patterns where stress can occur – this is to stop the garment from ripping when we put them under that stress. The trouser legs have a touch of ease added. So, this needs to be born in mind when you are walking your patterns!

Be sure to take note of any notches – also referred to as balance points! You can learn more about pattern symbols here.

Measuring Patterns

If you aren’t so sure about walking your patterns – lack of space can limit this if you only have a small desk to work on – then you can use the edge of your tape measure to check the seam measurements.

Measuring Seams - The Creative Curator

You can see from the photo above that I am using the tape measure on its edge! This is essential!

We don’t work with flat tape measures when truing up patterns due to possible inaccuracies!

You will need to true like this for every seam that needs to be trued and note down the measurements next to that seam. Again, don’t forget to factor in any ease that might be added to any of the seams.

Truing Up Draped Patterns

Draping a bodice block on a dress form

Truing in draping works the same way so if you have draped directly onto a body or dress stand, you need to consider how you will true up the drape.

One of the most important steps when it comes to truing your draping is to mark in both the straight grain line and the crossgrain before the draped fabric is taken of the model / dress stand.

Make sure to mark in the centre front and centre back too before removing from the model / dress stand.

You could either continue truing up on the stand, or, if you have pins, basting stitches and pen marks in place you could also take the drape off and true up your pattern on the flat.

Learn how to drape on a dress form here!

Seams That Need A Little Ease

How to sew a puff sleeve - sewing the side seam of your puff sleeve!

Ease is the extra ‘amount’ added to patterns for comfort. When it comes to truing a pattern though, we consider ease within seams, not the ease added for the overall fit of a garment. Learn more about ease in patterns here!

Outer Leg Seam

There is usually a centimetre ease added to the back trouser pattern around the high thigh point. This is to help the fabric as it strains over our legs when we sit or lunge, and lessens the possibility of it ripping.

Inner Leg Seam

Some designers also add a little ease to the back inside leg seam for the same reason.

Shoulder Line

There is always a little ease added to the back shoulder. This helps the fabric work round the shoulder, and let the front nicely.

Sleeve Cap

In order for a sleeve to fit nicely inside the armscye / armhole, and not looking flat, there is often ease added to the sleeve cap of the sleeve, between the front and back notches.


There is often a little ease also added to the back sleeve pattern around the elbow area. This is again to allow any strain on the fabric to not pull or rip the seam.

Truing Your Own Patterns

You now have an understanding of why we true our sewing patterns, and how. You’re now ready to start truing patterns for yourself.

Remember, it really isn’t as complicated as it sounds but if you do have any other questions, don’t forget to hit me up with them in the comments below!

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debbie mayo

Sunday 21st of May 2017

Very interesting! When I've made clothes from commercial patterns, I've had to go across different size lines so the clothes fit me; but until now i hadnt known about the ease on trousers etc nor the truing up bit... having been a bit of a "make it up as you go along" type if person its good to know how things should be done properly.

Eve Tokens

Wednesday 24th of May 2017

Ha ha, for many years I made it up as I went too Debbie! It was only after being 'formally educated' that I realised some of the areas I had been going wrong! ;)