Ultimate Trousers Sewalong No. 5: Getting the Right Fit

With a fitted pair of trousers like these it's really important to get the fit bang on. Because we're all different shapes and sizes you're probably going to find that the fit isn't perfect on you. If you've got a smaller waist you might find you need to bring in the side seams at the top. If you've got larger calves you might want to let the leg seams out slightly below the knee. And if you've got a full bottom you might find you have some gaping to fix at the centre back. We're going to guide you through how to fix some simple problems to help you get that perfect fit.

Let's start with a really common fit issue: bringing in side seams.

Taking in the side seams

A lot of people find in dressmaking that their body measurements don't easily correspond to the sizing the pattern is designed for. You might have a size 10 bust and waist, but size 12 hips. It means if the garment fits on the hips it will probably be too big on the waist, and that this extra fabric needs to be taken in.

It's a simple alteration to make, but always do this before you put the zip in. Put the trousers on inside out and pin them 1.5cm from the edge at the openings you have left at the top. So that you can stand up straight, ask someone pin for you.  You might need to pin only at the top at your waist, but depending how loose the trousers are you might find you need to carry on pinching out fabric further down the leg. One thing you must be careful with is making sure whatever you take in, grades gently back into the original seam line to prevent funny angles appearing.


Try and keep the amount of fabric you pin out even on both sides. Use a tape measure to double check this. Once you are pinned in and happy with the fit, use chalk or a washable fabric pen and mark your new side seam. You might want to do this once you have taken them off.


Take your trousers off, and with the front and bag legs pinned together, sew the right leg all the way up to the top.

The left leg is where we will insert the zip, so don't sew this side up yet! We will go through inserting the zip tomorrow, so hang tight until then.

Narrowing or expanding the calf area

Another common issue people can tend to have with tighter fitting trousers is the the width of the leg is not quite right. If the trousers are too tight around the calf they will ride up and it can be annoying and uncomfortable. If they are too loose they can feel like they are flapping around your ankles.

If your trousers are too tight, you can let the seams out a little bit. You have 1.5cm of seam allowance on both sides of the leg to play with. Unpick the side seams from the knee downwards. Pop the trousers on and ask someone to repin the side seams to a comfortable fit.  Then resew the legs with a smaller seam allowance.

If your trousers are too wide you might like to narrow them down a little bit. Put them on inside out and on both sides of your leg, pin out the excess fabric.


Take your trousers off again, leaving the pins in. Measure the amount of fabric you want to take out across the whole leg and divide it by two. At the bottom of the leg, mark this amount in from the existing line of stitching.


From this mark, draw a straight line up to the existing stitching at the knee. We do it this way because we want the line to be as straight as possible so that the trousers will hang correctly. Repeat this on the other side of the leg.


Then sew up the trouser legs using these new lines as your guide.



Unpick the first line of stitching and trim down the seam allowance to 1.5cm. Finish the new seam allowance to stop it from fraying. Then press the seams open.

Omitting the front darts

As mentioned in Tuesday's post, darts are there to add shaping to a garment. If we were completely flat there would be no need for darts, but as the female body has a lot of curves to it, the fabric has to be manipulated around the body in some way. As well as darts, shaping can also be achieved through the use of gathers and pleats.

We use darts in the Ultimate Trousers at the front and back. At the back they help to accommodate the bottom, and at the front, the tummy. If you are lucky enough to have a very flat stomach you might find you don't need the darts in the front and you could omit them completely.

If you do this you will need to draft a new facing pattern for the front. You can do this by tracing off the top of the front trouser to the same depth as the original facing, ignoring the darts. Then take the 1.5cm seam allowance off the centre front edge as this is cut on the fold.

Gaping at the centre back

If you have a bigger bottom or a back that curves inwards you might find you have some gaping at the centre back. This can be pinched out in much the same way as you would for the side seams. Put the trousers on inside out, pin out the excess fabric, mark it with chalk, then sew up your chalk line.

Things to check for

- Balance - are your side seams straight? If they pull forwards or backwards it is an indication that you need to add some width to the trousers. So if your side seams around your bottom are pulling towards the back, you might need to add some room into the back leg piece. You can do this by reducing the seam allowance on the back

- Level waistline - ladies with bigger bottoms might find that their trousers dip down at the back. This is because (as ladies who have to make this adjustment ourselves, we say this with love) the trousers are having to travel further around your bottom than they were designed to, which makes them too short. To combat this the best thing to do is to add some length to the centre back seam on your pattern, tapering it out to nothing at the side seams.

If you've found you have a fit issue that we haven't covered do ask us, we can help.
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