What does GSM tell you?
When a buyer asks how many grams a T-shirt is, the discussion often concerns GSM: the weight of one square meter of fabric. This is different from the total weight of a finished garment. Size, pattern and construction affect how much material a garment uses.
GSM is a useful specification, but it is not a quality grade. Fabrics with the same GSM can differ in thickness, softness and opacity because yarn, structure and finishing also matter. Make comparisons within a clearly defined material and construction.
Work backward from the wearing occasion
For an everyday summer T-shirt, priorities may include lightness, coverage and stability after care. A streetwear style with a pronounced silhouette may place more emphasis on structure and body. Neither brief has one universally correct GSM. The choice should support the product and the wearer.
Check light and dark colorways separately where relevant. A white version deserves particular attention to coverage. Neckline construction, shoulder shape and hem details also influence the finished impression; increasing fabric weight cannot solve every design issue.
Make the final comparison in a garment
Compare two or three material options close to your target. Record their appearance when laid flat, their shape on the body, movement and their condition after the agreed care procedure. Keep other variables as consistent as possible so a pattern change is not mistaken for an effect of fabric weight.
For quotation and approval, state the fabric condition to which the GSM specification applies and agree an appropriate tolerance. Retain the approved reference. The final choice should explain why the material suits the T-shirt, rather than simply which option has the largest number.