Fabric GSM Calculator: Convert, Measure and Estimate Fabric Weight

Fabric weight is written as grams per square metre (GSM) in China and as ounces per square yard in the United States, and both numbers describe the same cloth. The calculator below converts between the two units, works out the weight of a sample you cut and weighed yourself, and estimates how much fabric an order will consume. Everything runs in your browser and nothing you type is sent to us. When you want the number confirmed against the roll you would actually receive, send the style and we will quote weight and blend together.

What GSM measures, and what it does not

GSM is mass per unit area: how many grams one square metre of the cloth weighs. It is the fastest way to compare two fabrics of the same construction, and it is the number mills, labs and buying offices use on spec sheets.

It does not tell you how the cloth behaves on a body. Thickness, stretch, opacity and hand feel all depend on the fibre and the knit as much as on the weight, which is why two fabrics at 220 GSM can sit at opposite ends of a product range. We quote weight and blend as a pair on every spec we issue, because 220 GSM in nylon and 220 GSM in polyester are different fabrics that happen to weigh the same.

The conversion between g/m² and oz/yd²

One ounce per square yard equals 33.906 grams per square metre. The figure comes from the unit definitions: one ounce is 28.3495 grams and one square yard is 0.836127 square metres, so dividing one by the other gives 33.906. To convert in the other direction, divide the GSM figure by 33.906.

A worked example: a standard retail tee at 180 GSM works out to 180 ÷ 33.906 = 5.31 oz/yd². A heavyweight brushed fleece at 400 GSM is 11.80 oz/yd². If a spec sheet gives you ounces and you need grams, multiply by 33.906 instead; 8 oz/yd² is about 271 GSM.

Rounding is the only thing to watch. Some spec sheets round to one decimal, which moves a 180 GSM fabric between 5.3 and 5.4 oz/yd² depending on where the rounding happened. When a tolerance matters, ask for the weight in GSM rather than ounces, because GSM is the unit the mill weighs against.

How to weigh a sample without a GSM cutter

The second tab above reproduces the same measurement our own incoming inspection runs, minus the machinery. Cut a square of fabric with a clean edge — 20 cm × 20 cm is a convenient size — measure the sides carefully, weigh it on a scale that reads to 0.01 g, and divide the weight by the area. A 20 × 20 cm piece has an area of 0.04 m², so a reading of 7.5 g works out to 187.5 GSM.

Three habits make the reading trustworthy. Cut the piece away from the selvedge, because the edge carries a different weight from the body of the cloth. Lay the piece flat and measure it without stretching the fabric, because stretch changes the area. And weigh the piece on its own, not resting on the cutting mat or a paper label.

On our floor the incoming check is done with a circular cutter and a gram scale: each roll is weighed on arrival and any roll that falls outside ±5% of the agreed weight is rejected before it reaches cutting. The same arithmetic this calculator performs is what decides whether a roll enters production.

Which weight suits which garment

The table below lists the weight ranges we work to across the garment types we manufacture, with the ounce equivalent beside each one so you can read either unit. Every range here matches the fabric tables published on the T-shirt, hoodie and yoga wear manufacturing pages, where each range sits next to the fabric families it comes from.

From net area to what you actually buy

The third tab multiplies the net pattern area of a garment by the fabric weight to give the weight of one piece and of the whole order. That weight is what drives freight quotes and cost per kilogram, so it is the number most buyers want first.

What the calculator cannot show is the gap between net area and purchased length. A marker nests the pattern pieces side by side inside the roll width, and the spaces between pieces are cut away and scrapped, so real consumption is always higher than the net figure. How much higher depends on the style, the piece count and the width you buy. Send us the style and we will produce the marker, which turns the estimate into a purchase quantity you can plan an order around.

Why the same GSM can feel different on two fabrics

If you have ever held two 220 GSM fabrics that felt nothing alike, the fibre explains it. Nylon-spandex gives the softest hand feel and the best opacity for its weight, which is why a 220 GSM nylon legging is our reference spec for a premium legging. Polyester-spandex needs roughly 230 to 240 GSM to reach comparable coverage, but it dries faster, costs less and takes sublimation printing well. The same arithmetic, two different garments.

This is also why a weight tolerance is always written against a named fabric. When you brief a style, give us the weight and the blend together, or give us the hand feel you are after and we will propose the pair that gets there.

Sending a weight with your enquiry

A weight figure on its own does not give a factory enough to quote from. The enquiry that moves fastest includes the style reference or a link to the closest piece in our catalogue, the fabric weight and blend, the colours and the quantity per colour, and the size range. If you only have a target weight and a description of the garment, send that — we will come back with the fabric options we hold in that range and a sampling plan.

Sampling takes 3–7 working days from a confirmed design, and bulk production runs 15–25 days after the sealed sample is approved, excluding shipping. If you are planning a first order, the small batch ordering guide walks through how a 100-piece minimum splits across styles and colours.

Frequently asked questions

How do I calculate GSM from a fabric sample?

Cut a square with clean edges, measure both sides in centimetres, and weigh the piece on a scale that reads to 0.01 g. Divide the weight in grams by the area in square metres: a 20 by 20 cm piece covers 0.04 square metres, so 7.5 g on that piece works out to 187.5 GSM. Cut away from the selvedge, measure without stretching the fabric, and weigh the piece on its own. The Measure a Sample tab above does this arithmetic for you.

How many grams per square metre is one ounce per square yard?

One ounce per square yard equals 33.906 grams per square metre. The figure follows from the unit definitions: one ounce is 28.3495 grams and one square yard is 0.836127 square metres, so the ratio works out to 33.906. To go the other way, divide the GSM figure by 33.906. A 180 GSM tee is therefore about 5.31 oz/yd², and an 8 oz/yd² fleece is about 271 GSM.

Is a higher GSM always better?

No. Higher weight adds density, opacity and structure, but the right weight depends on the garment, the climate it is worn in and the silhouette it has to hold. A 140–160 GSM tri-blend tee is correct for a drapey fashion fit, while a boxy oversized tee needs 220–260 GSM to hold its shape. Weight also behaves differently by fibre: 220 GSM in nylon feels and covers differently from 220 GSM in polyester, which is why weight and blend are always quoted as a pair.

How do I convert a tee weight from oz to GSM?

Multiply the ounce figure by 33.906. A 4.5 oz/yd² tee is about 153 GSM, a 5.3 oz/yd² tee is about 180 GSM, and a 6.1 oz/yd² tee is about 207 GSM. If the spec sheet rounds to one decimal, the converted GSM can drift by a few grams in either direction, so for anything tolerance-sensitive ask for the weight in GSM, which is the unit mills weigh against on the floor.

How much fabric do I need for a 100 piece order?

It depends on the style, the fabric width and the marker, so there is no single number. The calculator above gives the net figure: net pattern area per garment multiplied by the quantity. Real purchase quantity is higher, because the marker wastes the gaps between pieces, and the waste depends on how the pieces nest inside your roll width. Send us the style and quantity and we will produce the marker, which turns the estimate into a purchase length you can plan around.

Why does the same GSM feel different on two fabrics?

Because GSM measures mass per area, not how the cloth is built. Fibre, knit construction and finishing all change the hand feel at the same weight. Nylon-spandex at 220 GSM is dense, smooth and opaque, while polyester-spandex at the same weight feels less substantial and needs roughly 230 to 240 GSM for comparable coverage. That is why a spec always names the blend next to the weight, and why we quote the two together on every fabric we offer.