Fabric GSM guide: what weight to choose for T-shirts, hoodies and more

GSM measures fabric weight in grams per square metre. See typical GSM ranges for T-shirts, polos, sweatshirts, hoodies and joggers, and how to write it in a tech pack.

Updated 1 October 2026 · By Hem Apparel

GSM stands for grams per square metre. It is the weight of one square metre of fabric, and it is the quickest way to describe how thick, heavy and warm a fabric will feel. Two white cotton T-shirts at 150 GSM and 250 GSM are effectively different products, with different costs.

Typical GSM ranges

These are general ranges, not standards. Fabric type, yarn, finishing and the mill all change how a given GSM feels.

What GSM changes

• Price: heavier fabric uses more yarn, so the cost per metre and the shipping weight go up.
• Drape: lighter fabric drapes and clings, heavier fabric holds a boxy shape.
• Season: lightweight is breathable for summer, heavyweight is warmer and more durable.
• Print results: very thin fabric can show ink through, and heavy fabric takes screen prints well.

How to write GSM in a tech pack

Write fibre content, fabric construction and weight together: '100% combed cotton, single jersey, 200 GSM'. Add a tolerance, because a mill will rarely hit the exact number. A tolerance of ±5% is commonly allowed, so ask your factory what they can hold.

Ounces and GSM

In the US, weight is often given in ounces per square yard (oz/yd²). Multiply by 33.9 to approximate GSM: 6 oz is roughly 200 GSM and 10 oz is roughly 340 GSM.

How to choose

1. Find a garment you like and check its weight, or ask the factory for a fabric swatch book.
2. Order swatches or a sample in two weights if you are unsure.
3. Confirm the final GSM with the factory before you approve the sample.
4. Record the exact fabric spec in your tech pack so bulk matches the sample.