What Does GSM Mean in Clothing? A Practical Guide to Fabric Weight

GSM means grams per square metre. It tells you how much a given area of fabric weighs, rather than the weight of the whole garment. A higher number means more weight in the same area, but it does not automatically mean better quality, a better fit or a warmer outfit.

You will see the number in T-shirt, hoodie and jogger descriptions, often without much explanation. It is useful once you know what you are comparing. Here is how to read it and put it to work when choosing everyday clothing.

What does the number actually measure?

Imagine two squares of fabric, each one metre wide and one metre long. If one weighs 155 grams, it is 155gsm. If the other weighs 300 grams, it is 300gsm. The area stays the same; the amount of weight changes.

That does not mean a 155gsm tee weighs 155 grams. The finished item uses a different amount of fabric depending on its size and shape, with additional weight from seams, trims and other details. Two sizes made from the same material can have the same GSM while weighing different amounts overall.

GSM is also different from thickness. Weight and thickness can be related, but a number on its own cannot describe how tightly the fabric is constructed or how much loft it has. Think of it as one line in the specification, alongside material, construction, fit and care.

What 155gsm and 300gsm mean within CARVÉ Core

The current Core listings give us three clear examples. These are specifications for the products below, rather than universal rules for all tees or hoodies.

Piece	Listed fabric weight	Useful starting point
Core CV T-Shirt in Black	155gsm	A lightweight tee to wear on its own or as a first layer.
Core CV Hoodie in Black	300gsm	A more substantial pullover layer.
Core CV Joggers in Black	300gsm cotton fleece	A fleece option for relaxed everyday outfits.

The hoodie fabric carries more weight per square metre than the tee fabric. It is not a claim that the hoodie is twice as warm, or that one piece will last twice as long. The joggers and hoodie share a listed weight, but have different shapes and purposes. Matching numbers do not make two garments interchangeable.

Why fabric construction matters too

Cotton describes a fibre. Jersey and fleece describe fabric constructions or finishes. Those are different pieces of information, and they work together when you assess a garment.

CottonWorks' guide to knitted fabrics explains that jersey is widely used for T-shirts and can be made in different weights. It also describes the napped interior associated with common fleece constructions. The surface and structure help explain why two cotton fabrics can feel different.

When shopping, look for photographs or descriptions of the inside as well as the outside. A smooth surface and a brushed interior tell you something the GSM figure does not. If the listing does not confirm a construction detail, ask rather than assuming that every garment at a particular weight has it.

Is a heavier T-shirt always better?

No. The useful choice depends on what you want the tee to do. If you dislike bulk beneath a close-fitting overshirt, chasing the highest possible weight may make the outfit less comfortable. If you enjoy a more substantial standalone tee, a heavier option may be worth trying.

Start with a garment you already like. Ask what you enjoy about it: the way it hangs, how it feels under a jacket, or the amount of fabric through the sleeves. If its weight is available, use that as a reference when comparing similar pieces. If it is not, those observations are still useful.

A lightweight tee can be a deliberate choice. Its suitability rests on your preferences and the complete garment, not on whether it reaches a supposed minimum number. There is no single GSM that every good T-shirt must have.

Does GSM tell you whether a white tee is see-through?

It cannot settle that question by itself. Colour, construction, fit and the light in which you wear the garment all affect its appearance. Do not treat a higher number as a guarantee of opacity.

If coverage is a priority, inspect the actual tee in daylight and try it in the way you intend to wear it. Check across the chest and shoulders as you move, because fabric pulled taut can look different from fabric hanging freely. Product photographs are useful, but cannot reproduce every lighting condition.

Choosing for a UK day out

For a day that moves between a chilly station platform and a warm café, consider the whole outfit. A lighter tee with a removable layer gives you options as the setting changes. A substantial hoodie may suit a relaxed afternoon, but still needs an appropriate outer layer if the forecast calls for rain or cold.

For travel or packing, remember that GSM is not the same as suitcase weight. The amount of fabric, hood, pockets and size all contribute to the finished garment. Choose the layers you need, then check whether they fit comfortably in your bag.

Fabric weight is useful for narrowing options within a similar type of clothing. It is less useful as a shortcut across completely different pieces, such as judging a T-shirt against a jacket.

Five questions to ask alongside GSM

1. What is it made from? Read the composition rather than relying on the weight.
2. How is the fabric described? Look for construction and lining information where available.
3. What job will it do? A first layer and a standalone top may suit different preferences.
4. Does the shape suit you? Check the size guide, shoulders, sleeves and length.
5. How will you care for it? Follow the individual garment instructions, not a routine inferred from GSM.

The current Core tees, hoodies and joggers list wash-cool and hang-dry care. Follow the label inside the item for any further instructions. Weight alone does not justify a hotter wash or a particular drying setting.

Choose the garment, not just the number

Use GSM to understand the fabric specification, then bring the decision back to comfort, fit and use. A number is most helpful when it explains a choice you are making, rather than becoming the entire reason for buying.

Explore CARVÉ Core to compare the current pieces. For the next part of the decision, our T-shirt fit guide explains what to check beyond the fabric weight.