Woven Fabric With No Stretch Relies on Construction, Not Elasticity
I wrote before about how spandex content decides the fit. Woven fabric like a dress shirt or a pair of slacks, though, plays by different rules. Fabric with almost no stretch cannot give at all, so construction ends up doing all the work. Looking back on years of making clothes, the parts shoppers rarely look at, seam allowance and stitch density, are what actually decide how long a garment lasts.
Seam Allowance Tells You If a Garment Will Last
Turn a garment inside out and look at the seam allowance, and you get a rough sense right away. At under 1cm, the seam is trimmed right to the cutting line, so the garment only works at exactly that size. There is no room for a tailor to let it out later, whether you gain weight or build muscle. At 2cm or more, there is enough extra fabric that a tailor can usually loosen the side seams or waist down the road. In a stretch of life where your body keeps changing from dieting or strength training, a garment with generous seam allowance simply lasts longer.

Stitch Density Tells You a Lot About Seam Quality
Look closely at a seam and you will also notice differences in stitch density. The tighter the stitches per inch, the sturdier the seam, and the better it holds up to repeated washing. When the stitches are spaced too far apart, a garment can look fine at first but starts unraveling after just a few washes. If you tug gently on a seam and it opens up right away, that is a sign of low stitch density.

3 Spots I Feel Before Buying a Woven Shirt
When I am shopping for a shirt, I feel for a gusset or pleat at the underarm, check whether there is ease at the sleeve cap, and see if the yoke, the back shoulder panel, is stitched twice. When those three spots are solid, the seams rarely give out when you raise your arms or move around.

This Is What I Look For Now
With my weight fluctuating these days, I lean toward clothes with generous seam allowance and tight stitching. Even if it costs a bit more upfront, I know from years of experience that being able to alter and keep wearing a garment later pays off in the end.
Even So, There Are Limits
That said, budget woven garments are often cut with barely any seam allowance to begin with, so no amount of careful shopping gives you room to let them out. None of this shows up from the label or the price tag alone, so in the end I always end up turning the garment inside out and feeling it with my own hands.
Wrapping Up
For stretchy knit fabric, blend ratio decides the fit. For woven fabric with no stretch, seam allowance and stitch density decide both fit and lifespan. If your body is still changing, I would suggest feeling the inside seam allowance and the stitching the next time you shop.