Shop for blank shirts long enough and you will see two kinds of numbers: "5.3 oz" on one shirt and "280 GSM" on another. They measure the same thing in different units. Once you know how to read them, you can compare almost any tee or hoodie on paper before you spend a dollar. Here is the plain-English version, with the shirts we actually print on in Paramus as examples.
What GSM means
GSM stands for grams per square meter. Cut a one meter by one meter square of the fabric, weigh it, and that is the GSM. A 180 GSM tee fabric weighs 180 grams per square meter, and a 280 GSM fabric weighs 280 grams for the same area. More grams in the same space means more cotton (or cotton and polyester), which almost always means a thicker, more opaque, more structured fabric.
American suppliers usually list the same thing in ounces per square yard, written as "oz." So when Gildan calls the 5000 a 5.3 oz tee, it means one square yard of that fabric weighs 5.3 ounces.
How to convert oz to GSM
One ounce per square yard equals about 33.9 grams per square meter. The Textile School unit converter and Fabric Almanac both use this factor. So:
- oz to GSM: multiply by 33.9
- GSM to oz: divide by 33.9
| Ounces per sq yd | About this GSM | What it usually is |
|---|---|---|
| 4.3 oz | 146 GSM | Lightweight or fashion tee |
| 5.3 oz | 180 GSM | Classic "heavy cotton" event tee |
| 6.0 oz | 203 GSM | Midweight premium tee |
| 6.5 oz | 220 GSM | Heavier premium tee |
| 7.6 oz | 258 GSM | Heavyweight streetwear tee |
| 8.2 oz | 278 GSM | Very heavy tee, or a light hoodie |
| 10 oz | 339 GSM | Heavyweight hoodie |
| 13.5 oz | 458 GSM | Extra-heavy premium fleece |
You will notice brands round a little differently. Lane Seven lists the LS17005 tee as 8.2 oz and 280 GSM, and Independent lists the IND5000P Legend hoodie as 13.5 oz and 460 GSM. Small differences like that come from rounding and from how each mill measures, so treat anything within about 5 GSM as the same weight.
What the common weights feel like
Numbers only help if you know what they feel like. Here are the shirts and hoodies in our online designer, grouped by weight, using the maker's listed numbers.
| Weight | Example in our designer | How it feels | Price for 1 (colored, front print) |
|---|---|---|---|
| 4.3 oz / about 146 GSM | Lane Seven LST002 mineral wash tee | Light, soft, a little drapey | $27.50 |
| 5.3 oz / about 180 GSM | Gildan 5000 | The classic event shirt | $23.00 |
| 6 oz / 200 GSM | Bella+Canvas 3010 | Sturdy, smooth, relaxed cut | $31.50 |
| 8.2 oz / 280 GSM | Lane Seven LS17005 | Thick, boxy, stands away from the body | $33.00 |
| 8 oz | Gildan 18500 hoodie | Everyday team and school hoodie | $41.50 |
| 10 oz / 340 GSM | Lane Seven LS19001 hoodie | Noticeably warmer and heavier | $47.50 |
| 11.5 oz / 390 GSM | Champion S101 Reverse Weave | Dense, classic heavyweight | $75.50 |
| 13.5 oz / 460 GSM | Independent IND5000P Legend | The heaviest hoodie we offer | $69.50 |
Prices are as of November 2026 and drop at 6, 12, 24 and 48 pieces. Clothing is not taxed in New Jersey.
What GSM does not tell you
GSM is useful, but it is not the whole story. Two shirts with the same GSM can feel very different because of:
- Yarn and knit. Combed, ring-spun cotton feels smoother than open-end cotton at the same weight. A tighter knit feels denser.
- Fiber blend. A 50/50 cotton-poly hoodie and an 80/20 hoodie at similar weights feel and age differently. More cotton is softer and breathes better; more polyester shrinks less.
- Fit. A boxy, drop-shoulder cut feels heavier and more "streetwear" than a fitted cut at the same weight.
- Finish. Garment dyeing and washing soften fabric and can make a heavy shirt feel broken-in on day one.
- Measurement. Some mills measure fabric before washing and dyeing, some after. That is one reason you see slightly different numbers for the same style, as charts like Yarnstick's GSM chart point out.
Which weight should you pick?
- Summer events, camps and races: 145 to 185 GSM. Cool, cheap and fine for a few wears. A performance polyester tee is another option.
- Staff and work shirts: 180 to 205 GSM. Durable without being hot behind a counter.
- Brand and merch tees: 200 to 280 GSM. People notice the weight when they pick it up, and it is part of what they are paying for. Our heavyweight vs regular tee guide goes deeper.
- Hoodies for a New Jersey winter: 270 GSM and up. Our Bergen County hoodie guide compares the options.
Reading a spec sheet in 30 seconds
When you look at a blank on a supplier site or in our designer, these are the lines worth reading, in order:
- Weight in oz or GSM. Convert if you need to, using the 33.9 factor above.
- Fiber content. 100% cotton, a CVC blend (mostly cotton with some polyester), a triblend or 100% polyester. This tells you more about feel and shrinkage than weight alone.
- Yarn. "Ring-spun" or "combed" usually means smoother and softer. "Open-end" is sturdier and a bit rougher.
- Fit. Classic, retail, relaxed, boxy or oversized. Check the size chart's chest width, not just the size letter.
- Finish. Garment-dyed, pigment-dyed and mineral-wash shirts look and age differently. Our dye guide explains each one.
A quick example: the Lane Seven LS17005 lists 8.2 oz, 280 GSM, 100% combed cotton and an oversized fit. From that one line you can tell it will feel thick, smooth and boxy, before you ever touch it.
Feel it before you order a batch
The fastest way to learn GSM is to hold two weights side by side. Since we have no minimum, you can order one of each in the designer and compare before you place a big order. If you are trying to match a shirt you already own, send us the tag details and we will suggest the closest blank we can print on.