What Is GSM in Fabric? Full Form, Formula and the Right GSM for Kids' Clothes

GSM in fabric stands for grams per square metre. It is the weight, in grams, of one square metre of a fabric, and it is the single most useful number for judging how light, heavy, warm or sturdy a garment will feel. A 120 GSM fabric is light and airy, a 180 GSM fabric is a standard T-shirt weight, and a 240 GSM fabric is a mid-weight knit like French terry. You calculate it with a simple formula: GSM = (weight of a fabric sample in grams ÷ its area in cm²) × 10,000.

For children's clothes in India, there is no single "best" GSM. A toddler in Chennai in April needs something very different from a five-year-old on a Delhi school morning in January. Below, we explain what GSM means, how to calculate it, what common numbers like 120, 180, 200, 400 and 500 GSM actually feel like, and the GSM range we would pick for kids' T-shirts, pants and sweatshirts in each Indian season. We are a pure cotton kidswear manufacturer in Tiruppur, so this is written from the factory side of the label.

In this article

• What is the full form of GSM in fabric?
• How do you calculate fabric GSM? (formula and worked example)
• What do 120, 180, 200, 240, 400 and 500 GSM mean?
• What is the right GSM for kids' clothes in India?
• Is higher GSM better quality?
• How can you check GSM before you buy?
• FAQ

What is the full form of GSM in fabric?

The full form of GSM in fabric (and in cloth or clothing) is Grams per Square Metre, sometimes written as g/m² or gsm. It tells you how much one square metre of that fabric weighs. If a label says "240 GSM", a piece of that fabric one metre long and one metre wide weighs 240 grams.

Think of it like paper. Thin printer paper is around 70 to 80 GSM, while a greeting card is much heavier. Fabric works the same way: the higher the number, the more cotton is packed into the same area.

A few things GSM is often confused with:

• GSM is not thickness. It is weight per area. A dense, smooth fabric and a loose, fluffy fabric can have the same GSM but feel completely different.
• GSM is not yarn count. Yarn count (for example "30s" cotton) describes how fine the thread is. Finer yarn usually makes a lighter fabric for the same knit, which is why we explain the two together in our post on why 30s combed cotton suits kids' pants.
• GSM is not thread count. Thread count is used for woven bedsheets and counts threads per square inch. GSM is used for knits like T-shirts and sweatshirts, and also for towels and many woven fabrics.
• GSM does not tell you the fibre. A 180 GSM polyester and a 180 GSM cotton weigh the same per metre but behave very differently on a child's skin in Indian heat. Always read the fibre content too.

How do you calculate fabric GSM? (formula and worked example)

There are two standard ways, both used in garment factories.

Method 1: the GSM cutter (how factories do it)

1. Lay the fabric flat on a cutting pad, without stretching it.
2. Use a round GSM cutter, which cuts a disc of exactly 100 cm² (one hundredth of a square metre).
3. Weigh the disc on a precision balance that reads to at least 0.01 g.
4. Multiply the weight by 100. A disc weighing 2.40 g means the fabric is 240 GSM.
5. Repeat from 3 to 5 different spots and take the average, because fabric is never perfectly even.

This is the method described in most textile training material, including Online Clothing Study's guide to calculating fabric GSM.

Method 2: the fabric GSM calculation formula

If you do not have a cutter, cut a neat rectangle, measure it, weigh it and use:

GSM = (sample weight in grams ÷ sample area in cm²) × 10,000

Worked example: you cut a 20 cm × 20 cm square from a fabric offcut. Its area is 400 cm². It weighs 9.6 g on a kitchen scale.
GSM = (9.6 ÷ 400) × 10,000 = 240 GSM.

Two practical tips for parents and small sellers trying this at home:

• Use a bigger sample. A 10 cm square of T-shirt fabric weighs under 2 g, and most kitchen scales only read to 1 g, so your answer could be off by half. A 20 cm or 25 cm square gives a far more reliable number.
• Weigh only one layer of fabric. Seams, prints, labels and ribbing add weight that is not part of the fabric's GSM.

If you see fabric weight in ounces (common on US websites), convert it like this: GSM = oz per square yard × 33.9. So 6 oz is about 203 GSM, and 240 GSM is about 7.1 oz.

What do 120, 180, 200, 240, 400 and 500 GSM mean?

Here is a quick lookup table for the GSM numbers people search for most. Ranges are typical industry values for cotton fabrics; exact feel also depends on knit, yarn and finishing. As a broad rule, fabric under about 150 GSM is considered light, 150 to 250 GSM medium and above 250 GSM heavy (Sew Guide).

So when someone asks "what does 500 GSM mean?", the honest answer is: a very dense fabric, usually a towel or blanket. For clothing, the useful range for Indian kids sits roughly between 120 and 320 GSM.

What is the right GSM for kids' clothes in India?

Children are on the move all day, get warm quickly during play, and often kick off layers at night (we wrote about why kids kick off blankets). So for most of the year in India, lighter to mid-weight cotton beats heavy fabric. This is how we would choose, garment by garment and season by season.

All figures in GSM, 100% cotton. "South and coastal" means places like Chennai, Bengaluru, Kochi and Mumbai; "north and hills" means places like Delhi, Lucknow, Chandigarh and hill stations.

T-shirts: 140 to 180 GSM for most of the year

A 180 GSM single jersey is the common standard for a good T-shirt, and many brands drop to 160 GSM to save cost (Sew Guide). For a child in Indian summer, the 140 to 180 range is the sweet spot: light enough to breathe, heavy enough that a white tee is not see-through and the neckline survives daily washing. Go a little heavier (around 200) for full sleeve tees worn under a sweatshirt or in an air-conditioned classroom. Browse our cotton T-shirts for kids for everyday options.

Pants, joggers and shorts: why we chose 240 GSM French terry

Bottoms take the most punishment: crawling, sliding, sitting on school floors. That is why we make our knit pants, joggers and shorts in 240 GSM cotton French terry, a knit with a smooth outer face and soft loops inside. The loops trap a little air, so the fabric stays comfortable across a wide temperature range: warm enough for a Delhi December evening, still breathable through a Chennai afternoon. Our dark green striped French terry pants, red striped pants and blue striped pants are all 240 GSM, with an undyed inner face so no dye touches the child's skin, and they are compacted and pre-shrunk in our own factory to keep shrinkage under 5%. If you want plain basics, our grey 240 GSM joggers use the same fabric with ribbed cuffs. You can read more about the fabric itself in our manufacturer's guide to French terry.

240 GSM French terry · 1 to 8 years

Dark Green Striped French Terry Pants

Undyed inner face, knee pocket, pre-shrunk to under 5% shrinkage. A forgiving dark colour for park days.

₹799 See sizes →

For hot summer days outdoors, a lighter woven cotton pant is the better choice; our full range of cotton pants for kids includes both knit and woven styles, and our manufacturer's guide to cotton pants for kids explains how to pick between them.

Co-ord sets: match the GSM to the season

For summer, look for a light jersey T-shirt and shorts set. Our Sunny Side Up set is made from lightweight, sweat-wicking pure cotton for exactly that. For cooler months or AC-heavy days, a 240 GSM French terry set such as our Football Collection co-ord set has more body and drape. See all cotton co-ord sets.

Sweatshirts and winter wear: heavier only where it is truly cold

In Bengaluru or Chennai, a 240 GSM cotton sweatshirt over a T-shirt is usually all a child needs on a cool morning. In Delhi, Punjab or the hills from December to January, step up to a fleece-lined 280 to 350 GSM sweatshirt for outdoors and use layers rather than one very heavy piece, so you can take one off when the sun comes out. Browse our sweatshirt sets for kids, and see our tips on layering cotton for winter nights.

Is higher GSM better quality?

Not automatically. Higher GSM means more fabric per square metre, which usually means more durability and less see-through, but quality also depends on:

• Yarn quality. Combed and super combed cotton removes short fibres, so the fabric pills less and feels smoother at any GSM. Our post on combed cotton meaning explains why.
• Knit structure. A 240 GSM French terry and a 240 GSM interlock feel very different; one has loops inside, the other is smooth on both faces.
• Finishing. Compacting, pre-shrinking and biowashing change how soft a fabric feels and how much it shrinks, without changing the label GSM much.
• Fibre. A heavy polyester fabric traps heat. For Indian kids, a lighter 100% cotton almost always beats a heavier synthetic.

A stiff, thick feel in the shop is not a reliable guide either, because finishing can change how a fabric feels on day one. A stated GSM on a 100% cotton label is a more honest signal than "feels thick". We cover this in more depth in lightweight vs heavyweight clothing for kids.

How can you check GSM before you buy?

1. Read the description. Serious manufacturers state GSM and fibre. If both are missing, ask the seller.
2. Do the light test. Hold a single layer up to a window. Light fabrics (under about 150 GSM) show a lot of light; mid-weights show a soft glow; heavy knits are nearly opaque. For white school wear, avoid anything you can read through.
3. Stretch and release. Pull a knit gently sideways. Good fabric springs back. Fabric that stays stretched will bag at the knees.
4. Check the inside. On French terry, the loops should be even and firmly knitted, not loose and snagging.
5. Match it to your city and season using the table above, not to the price tag.

240 GSM French terry · 1 to 8 years

Red Striped French Terry Pants

The same mid-weight, all-season fabric with an undyed cotton base. Easy to pair with white or grey tees.

₹799 See sizes →

Lightweight summer cotton · 1 to 8 years

Sunny Side Up T-Shirt and Shorts Set

Lightweight, sweat-wicking 100% cotton with elastic waist shorts. OEKO-TEX Standard 100 certified.

₹799 Shop the set →

Frequently asked questions

What is the full form of GSM in cloth?

GSM stands for grams per square metre. It is the weight of one square metre of the cloth in grams, and it is the standard way to describe how light or heavy a fabric is.

Is 180 GSM good for a T-shirt?

Yes. 180 GSM is the common standard for a good cotton single jersey T-shirt: opaque, durable and still breathable. For kids in peak Indian summer, 140 to 160 GSM can feel cooler; for winter base layers, 180 to 200 GSM works well.

What does 200 GSM mean?

200 GSM means one square metre of the fabric weighs 200 grams. It is a medium-heavy weight, used for heavier T-shirts, polo tees and light sweatshirts, and suits full sleeve tops for AC rooms and mild winters.

What does 500 GSM mean?

500 GSM is a very dense, heavy fabric, typically a thick bath towel or blanket. It is far too heavy for children's everyday clothing in India.

What GSM is best for kids in Indian summer?

For T-shirts, 140 to 180 GSM in 100% cotton. For bottoms worn outdoors, light woven cotton; for indoor play and AC rooms, a 240 GSM French terry is comfortable because its loops let air move.

How do I calculate the GSM of fabric at home?

Cut a 20 cm by 20 cm square (400 cm²) from an offcut, weigh it in grams, then use GSM = (weight ÷ 400) × 10,000. A square weighing 9.6 g is 240 GSM.