Tilly and the Buttons: Fitting the Thea trousers

Are you planning on making the Thea trousers and want some extra help on how to get a great fit? Then look no further as this post is for you.

Thea is a pair of high waisted, wide leg trousers with a choice of two lengths and multiple pocket variations. As we're all different shapes and sizes, there are various adjustments we can do to improve the fit of our me-mades. In this blog post we're going to cover the most common adjustments you may want to consider making to your Thea trousers, but bear in mind you probably won't need to do all of them, or even any at all!

In this post we're going to cover:

Making a toile
Choosing your size
Lengthening or shortening pattern pieces
How to combine pattern sizes
Other common trouser fitting adjustments

Should you make a toile?

A toile - or a "muslin"- is an initial mock-up of your garment in fabric you don't mind using for testing purposes. A toile is a great opportunity to test the fit of a sewing pattern, as well as practising a technique, like inserting a zip or sewing a welt pocket, before you cut into your nice fabric. Pick a fabric with a similar weight and drape to the fabric you have in mind for your final project to get the best results.

Now, making a toile isn't absolutely necessary on all projects, but it is usually a good idea for trousers. We would definitely recommend making a toile for the Thea trousers, particularly if you're not sure what fitting adjustments you may need to make - or at least considering your first pair a "wearable toile". If you don't have much suitable fabric to hand, you can make a shorter version of the trousers that end above the knee so you can test the fit around the waist, crotch and hips.

We have a comprehensive blog post about toile making. Go check it out if you want to find out more!

Choosing your size

Thea includes all 15 sizes in our range. Pattern sizes 1-6 (UK 6-16) and 7-15 (UK 18-34) have been drafted, fitted and graded separately to create a better fit. For this reason, you may notice the proportions change in the measurements chart and the shaping is slightly different on the pattern pieces – sizes 7-15 include slightly more room at the waist, a deeper crotch and a bit more space for a fuller tummy.

To find your size, using a flexible tape measure, measure the circumference of your:

Waist - where you bend at the side
Hips - the fullest part - it helps to turn to the side and look in a mirror to see where this is

Check the tape measure is sitting level with the floor - it can help to turn to the side and look in a mirror to check.

Thea trousers body measurements and finished garment measurements chart

Circle your waist and hip measurements on the ‘Body Measurements’ chart in the pattern instructions. If your measurements all fall into one size, then this is the size you'll cut.

However, it's common for your measurements to fall into different sizes too. In fact, most people's do! You can create a bespoke fit for you by combining sizes. We'll come to that later, but first...

Lengthening or shortening pattern pieces

Our patterns are drafted for a height of around 5"5 (165cm). If you're particularly taller or shorter than this, or know you have a long or short torso or legs, you can change the length of the pattern pieces to fit you better. You can also change the length of the trousers or the rise to suit your own personal style.

We have a blog post dedicated to explaining how to lengthen or shorten pattern pieces. It talks you through the process, step by step, so take a look if you want more info.

If you do make an adjustment to the length of a pattern piece, remember to make the exact same adjustment to any pattern pieces that it will join. For example, if you shorten the rise on the front leg, make sure the same adjustment to the back leg, so the seams end up the same length.

We have included the following sets of lengthen or shorten lines on the Thea pattern pieces:

Diagrams showing how to lengthen or shorten the Thea trousers front leg pattern piece by Tilly and the Buttons

1) Leg (crotch)

The Thea trousers are high waisted, and designed to sit at the natural waistline i.e. where you bend at the side.

If you are tall or short overall and usually find trousers come up a bit too high rise or low rise for you, you can lengthen or shorten the crotch using the set of lines marked "lengthen or shorten here" on the upper part of the front and back leg.

2) Leg (below knee)

If you have particularly long or short legs, you can lengthen or shorten the pattern along the set of lines marked "lengthen or shorten here" on the lower part of the front and back leg.

The inside leg measurement for the Thea trousers is 62cm (24 1/2in) for the cropped version and 78cm (30 3/4in) for the full-length trousers. Compare this to your own inside leg measurement before you decide whether to lengthen or shorten the legs. If you're not sure if you need to shorten them, leave them as they are and shorten them at the hemming stage if you need to. The Thea trousers have a generous 5cm hem, which gives you a bit of wiggle room to decide on the hem length once you've almost finished the trousers and are able to try them on.

How to combine pattern sizes

The Thea trousers are fitted at the waist and high hip. As the trousers are reasonably fitted at the top we recommend choosing a size based on your waist and hip measurement from the body measurements chart. If these measurements fall into different sizes, you can grade between these areas to get a bespoke fit for your exact body measurements. Check out our blog post which explains how to combine sizes.

Diagram showing how to combine sizes for Thea trousers

If you want to combine sizes between the waist and the hips on the Thea trousers, you will need to adjust the front and back legs, in addition to the pocket bag and pocket lining pieces. Here's how you do it...

Cut out the front leg in the bigger of the sizes you wish to combine. Place the front leg on top of the pocket bag. In this example I am going to grade between a size 5 at the waistline and a size 6 at the hips. Pin the pieces together along the size lines for the size you want for the waist (so in this example a size 5), lining up the notches at the hip and waistline.

Slip some paper underneath the side seam and stick it to the pocket bag - we're going to adjust this piece first. Starting at the top left corner of the pocket bag, draw a new side seam line from the waistline to the hip notch for the sizes you want, and then carry on until you're in line with the bottom of the pocket bag.

The next step is to make sure the new side seam shape is transferred across to the pocket bag. How you do this will depend on whether you're grading to a bigger or smaller size at the hips, but you can either draw down the side of the side seam onto the paper underneath to get the new shape, or trace over the new side seam with a blunt tracing wheel (or stick a pin along the new side seam line every 1cm (3/8in) or so). Remove the front leg and connect the new side seam line to the bottom of the pocket bag, and re-draw the notches.

All that's left to do is transfer this new shape across to the front leg, back leg and front lining pieces! Place them on top of each other, matching notches, and add/remove width (depending on the sizes you're combining) so all pieces match.

Lastly, cut the waistband pieces to match the size of the waistline on your leg pieces.

Common trouser fitting adjustments

Now, I'm well aware this is potentially the section you have scrolled to look at first and are now thinking, "Wait, where are the tutorials on how to adjust the crotch/tummy/butt?!".

And to this I say relax, we have a whole blog post which covers the most common fitting adjustments for trousers. Full tummy? Flat seat? Don't worry, we've got you covered. Go check it out!

And that's it! Remember, when it comes to fitting trousers a little adjustment goes a (very) long way. Start by adding or subtracting a small amount and take it from there.

Please tag us on Instagram @TillyButtons with the hashtag #SewingThea. We can't wait to see your gorgeous Thea trousers!