T-Shirt Fit: The Four Points That Decide Everything
Two shirts labelled the same size can fit completely differently, because a size label is a manufacturer's shorthand and not a measurement. What actually determines fit is four seams and one amount of room. Learn to look at those and labels stop mattering.
1. The shoulder seam
This is the one that cannot be adjusted and the one most people get wrong.
On a set-in sleeve — the standard construction, where the sleeve is sewn into a curved armhole — the seam should sit at the outer edge of your shoulder bone, where the flat top of the shoulder starts to turn down into the arm.
- Seam inboard of that point, on top of the shoulder: the shirt is too small, and the sleeve will pull when you reach forward.
- Seam hanging down the arm: the shirt is too big, and the sleeve head will collapse into a soft fold that reads as sloppy.
Two exceptions. Drop-shoulder shirts are designed with the seam well down the arm — that is the style, not a fitting error. And raglan sleeves have no shoulder seam at all, running diagonally to the collar instead, which makes them more forgiving across a range of shoulder widths.
2. Where the sleeve ends
For a short sleeve, aim for roughly the midpoint of the bicep, or a little below.
Shorter than that starts to look like an athletic cut, which is a deliberate choice but a narrow one. Longer than the elbow crease turns the shirt into an accidental three-quarter sleeve and shortens the arm visually.
The sleeve opening matters as much as the length: it should follow the arm loosely without gripping it. A cuff that leaves a mark is too tight; one that flares is too wide.
3. Body length
The rule depends on what you plan to do with the hem.
Worn untucked: the hem should finish somewhere between the top and the middle of your trouser fly, and cover your belt. Shorter and it rides up when you raise your arms; longer and it starts to read as a tunic.
Worn tucked: you need noticeably more length, enough that the shirt stays tucked when you sit and reach. A shirt cut for untucked wear will pull out repeatedly.
4. Chest and body room
Use the pinch test. Standing relaxed, take hold of the fabric at the side of your chest and pull it away from your body.
- Roughly two to four centimetres of spare fabric on each side is a regular fit: it skims without clinging.
- Less than two is a slim or athletic fit, and it will show every detail underneath.
- More than five or six is a relaxed or boxy fit, which only looks intentional in a heavier fabric that can hold the shape. In a light fabric the same amount of room just looks like the wrong size.
The interaction nobody mentions
Fit and fabric weight are not independent. A boxy cut in a lightweight jersey collapses against the body and looks baggy; the same cut at 220 GSM stands away and looks deliberate.
If you like a relaxed silhouette, the fabric has to be heavy enough to carry it. If you prefer a slim silhouette, lighter fabric drapes more comfortably and does not add bulk.
The ten-second mirror check
- Look at the shoulder seams — both at the shoulder edge?
- Raise both arms overhead — does the hem lift above your waistband?
- Reach across your body — does the shoulder pull?
- Pinch the side of the chest — how much spare fabric?
A shirt that passes all four is the right shirt, whatever the label says.