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No single fabric GSM suits every legging or sports jersey. GSM (grams per square metre, the mass of a given area of fabric) does not on its own decide thickness, warmth, durability or whether a garment is see-through. Fabrics of the same weight can differ in yarn and structure, so coverage and appearance are checked on a sample in the intended colour, fit and movement. GSM remains useful for describing a material and comparing it with an agreed reference.
You can specify a target weight with an agreed tolerance once the material is established. While you are still choosing the fabric, a range or a reference garment can be more useful. Either way, describe the construction, colour, intended fit and performance alongside the number.
Why equal weights can look different
Two fabrics with the same GSM can use different yarns and structures. A smooth closed knit, an open mesh and a brushed fabric can have very different surfaces and thicknesses at similar weights. A double knit is not automatically more opaque than every single knit, and a warp knit does not solve coverage in every case.
The shape of the garment also changes the impression. A fabric may look fluid in a loose jersey and taut across fitted leggings. Drape depends on flexibility and construction as well as weight. Compare the garment itself rather than assuming a heavier fabric will always hang more firmly or last longer.
Check colour and extension together
Light colours and white areas can show contrast underneath, so include the colourways where coverage is most at risk. In ordinary sublimation on a white base, areas without printed dye stay the colour of the base fabric. A dark graphic can change how the garment looks, but sublimation does not add an opaque layer.
Stretch can open up the structure and change how a fabric covers. Assess the intended fit and movement: a flat swatch cannot show how a legging behaves in a squat or how a jersey looks stretched across the shoulders. Wet conditions can also change appearance, so include them where the garment will be used wet.
Make the sample comparison repeatable
| Check | Record so the result can be compared |
|---|---|
| Fabric identity | Supplier reference, composition, structure, colour and measured or stated GSM |
| Coverage at rest | Lighting, contrasting background and the area assessed |
| Coverage in use | Garment size, fit, movement or defined swatch extension |
| Wet appearance, if relevant | How the sample was wetted and assessed |
| Drape | Worn appearance, movement and comparison with the reference garment |
| Printed appearance | Fabric and process used, including fine detail and white areas |
| After care | Agreed washing and drying conditions and changes observed |
Use the same lighting and background for every comparison. For a worn sample, agree a suitable assessment with the wearer. A swatch fixture helps compare fabrics without relying only on a subjective fit check. Record the outcome, with photographs where useful. This is a practical selection procedure, not a named laboratory opacity standard.
If coverage fails, look at the fabric, colour, fit, panel design and lining together. A higher GSM may help in a particular construction, but it is not a guaranteed remedy and can change comfort and drape.
Connect weight to the buying decision
A jersey brief might ask for a light fabric with acceptable coverage in the white body panels and clear sponsor detail. A legging brief might put coverage under extension and recovery ahead of minimum weight, and a warm-up layer might put body and feel first. Requirements like these tell the factory what the weight has to achieve, without suggesting that one published GSM band suits every product.
For a confirmed order, record the selected fabric and its agreed weight tolerance in the specification. Fabric weight can be checked on a sample of known area under agreed conditions. That confirms the weight, but garment coverage and appearance still need their own assessment.
Use the fabric brief to request options and the stretch guide to define movement and recovery. For sublimated designs, approve the appearance on the production material using the colour and print reference guide.
Questions and answers
What GSM should I specify for sports leggings?
No single GSM suits all sports leggings, so specify what the weight must achieve rather than copying a published band. A legging brief might put coverage under extension and recovery ahead of minimum weight. Give a target weight with an agreed tolerance when the material is established, or a range or reference garment while still choosing, and describe the construction, colour, fit and movement alongside the number.
What GSM is right for a sublimated sports jersey?
The right GSM for a sublimated sports jersey depends on the fabric's structure, colour and fit, so no single weight applies to every jersey. A jersey brief might ask for a light fabric with acceptable coverage in white body panels and clear sponsor detail. In ordinary sublimation on a white base, unprinted areas stay the base colour and the dye adds no opaque layer, so check coverage and print detail on the fabric itself.
How can I test whether light-coloured leggings are see-through?
Light-coloured leggings need a coverage check both at rest and in use, in the colourway that poses the greatest risk. Record the fabric reference and GSM, use consistent lighting and a contrasting background, and assess the garment in the intended size during movements such as a squat, or with a defined swatch extension. Add wet conditions if relevant, and repeat after the agreed washing and drying.