Thank you for your suggestion! We all go through weight fluctuations in life, so it stands to reason our clothes should be able to fluctuate with us.
How to upsize clothes:
Introduction:
There are many different ways to make a garment larger. The following list is not exhaustive, just a few ideas to get you started.
Grading patterns:
If you're making your own clothes, it's always useful to know how to modify a sewing pattern. The easiest way to adjust a pre-existing pattern to your size is slash and spread grading. First, you need to define which spots on the pattern need extra space. You then cut your pattern in that spot, and slide the resulting pattern pieces away from each other until you've got the size you need. Use paper to fill in the gaps. To ensure the resulting pattern makes for well-fitting clothes, make a mock-up and add, move, or remove darts where necessary to adapt it to your body type.
(Image source) [ID: a diagram of slashing lines on a pattern block for a dress, bodice, skirt, sleeve, and a pair of pants.]
To make your clothes easier to let out in the future, make sure to provide ample seam allowance when cutting out your pattern pieces. This surplus fabric has several different uses, including giving you some wiggle room for when you need to size up your garment.
Now, let's take a look at pre-made garments.
Lengthening clothes:
A garment that's too short on you is easy to modify. Just add more material!
If it's a skirt or a dress, add ruffles to the bottom. Ruffles are easy to make by hand or with a sewing machine. You could also add lace, or wear the item with an underskirt.
As for shirts, sewing an extra layer to the bottom edge is the easiest way to go, too. You could even combine two shirts into one to get an extra long shirt.
Another option is to cut your item in two and insert extra fabric between your separated garment parts.
(Image source) [ID: a pair of blue pants with cuffs sewn onto the bottom of the legs to lengthen them. The cuffs are made out of a fabric with a blue and brown geometric print.]
(Image source) [ID: a before and after picture of a red t-shirt that was lenghtened by adding in a patch of colourful fabric at the waist.]
Letting out seams/darts:
Remember how we made sure to have ample seam allowance earlier? When a garment has surplus fabric in the seams and you only need a little extra space, you can undo the seams of your garment and sew them back together again, this time with a smaller seam allowance than before. The Spruce Crafts has a pretty good tutorial on how to let out seams. You won't be able to make major size changes using this technique, but if you only need a few centimetres, this is a good way to go.
A lot of garments also have darts. Darts are fabric folds that are sewn down in strategic places to help the fabric follow the body's curves. If a dart doesn't fit you the way you want it to, then unpick the dart and try on the garment. Either leave the dart open, or pin the dart in place however you want it, then take off the garment again and sew the dart back together.
Be careful not to rip the fabric when using a seam ripper. Also note that removing entire darts may change the garment's fit.
You can also add custom darts to achieve a better fit, but that's a topic for another time.
(Image source) [ID: twelve different types of darts on a feminine bodice block.]
Adding extra fabric to your garment:
If we need to add more room than seam allowance or darts can provide us with, we need to add extra material. Remember those slashing lines we looked at earlier? If you're working with a pre-existing garment rather than a pattern, those are the perfect places to chop up your clothes and add in extra fabric.
Check your sewing stash for fabric that's similar in weight and material to your original garment, or go thrift shopping for an item you could use to upsize your garment. Long skirts and maxi dresses are a great source of fabric for alterations like these!
Lace inserts are also a fun choice to add some room, and if you're working with a knit item, you could even knit or crochet your own custom insert.
Define the area where you want to add extra fabric on your item, and measure how much you need. Draw a straight line on your garment with chalk/soap. Make sure the line doesn't cross any important structural or functional parts of your garment like darts or button holes: refer to the slashing diagram we saw earlier if you're not sure what spot to pick. Cut the line open (or unpick the seam if it's situated on a seam), and add in your extra fabric. Finish off your new seams so they don't unravel later on, and you're done!
You can add straight strips of fabric for extra width or length, or you could use flared panels or even godets to make your item flair out.
Want to see this technique in action? Check out this video by Break n Remake:
Some ideas:
This Pinterest user cut a straight line down the front of a t-shirt and inserted a lace panel to add extra width in the front of the garment.
(Image source) [ID: a blue t-shirt with a panel of dark blue lace added in at the centre front.]
Busy Geemaw cut open the side seams of a shirt and used flared panels to add some extra width in the bust and hip area.
(Image source) [ID: a green and white long-sleeved shirt with a striped flared panel in matching colours inserted at the side seam.]
This person added a panel to the sides of a pair of jeans to give them more space in the hip area. You could easily use a long straight panel or a panel that flares at the bottom to resize the entire garment instead of just the hips, or use a wide piece of elastic for extra stretch.
(Image source) [ID: a side view of a pair of light blue jeans with a dark blue wedge-shaped denim insert running down from the waist and ending above the knee.]
This person added a godet in the back of their shirt in order to get more space in the back.
(Image source) [ID: a blue and white plaid shirt with a white lace godet inserted in the back.]
Blue Corduroy enlarged a pair of shorts by opening up the side seams and adding in strips of fabric.
(Image source) [ID: blue denim shorts with a floral fabric insert at the side seams.]
You don't need to resize the entire garment if you don't want to. For example, One Brown Mom turned this ankle-length skirt with a too small waistband into a well-fitting knee-length skirt by taking advantage of the skirt's flared shape.
(Image source) [ID: a woman wearing a black shirt and a brown tartan knee-length skirt.]
Conclusion:
Throughout our lives, our weight will fluctuate and our bodies will change. There's no shame in this: it's just a fact of life. Therefore, knowing how to upsize an item that is too small for you is a useful skill to learn.
