Ounces vs. GSM: T-Shirt Fabric Weight Conversion Guide
If you've gotten a quote from one supplier in ounces per square yard (oz/yd²) and another in GSM (grams per square meter), you've hit the most common point of confusion when ordering blank tees wholesale. Both measure the exact same thing — fabric weight — just in different units. Get the conversion wrong and you can end up ordering a fabric that's noticeably lighter or heavier than you intended. Here's how to convert between them, how many grams an actual t-shirt weighs, and which weight to pick for your project.
Ounces vs. GSM: The Conversion Formula
Ounces per square yard and GSM are both fabric density measurements — they just use different units of mass and area. The standard conversion is:
GSM = oz/yd² × 33.906
oz/yd² = GSM ÷ 33.906
Most U.S. mills and some import suppliers quote weight in ounces, while international suppliers and spec sheets — including most Peruvian and European mills — quote in GSM. Neither unit is more accurate than the other; you just need to convert before comparing two quotes side by side.
Ounces-to-GSM Conversion Chart
| Ounces (oz/yd²) | GSM (g/m²) | Typical Category |
|---|---|---|
| 4.0 oz | ~136 GSM | Lightweight |
| 4.5 oz | ~153 GSM | Lightweight |
| 5.0 oz | ~170 GSM | Midweight |
| 5.5 oz | ~186 GSM | Midweight |
| 6.0 oz | ~203 GSM | Heavyweight |
| 6.5 oz | ~220 GSM | Heavyweight |
| 7.0 oz | ~237 GSM | Heavyweight interlock/terry |
For the full breakdown of what each weight range feels like and when to use it, see our blank tee GSM guide.
How Many Grams Does an Actual T-Shirt Weigh?
GSM measures fabric density, not the finished garment's total weight — but buyers often want to know the real number for shipping and landed-cost math. A finished adult medium tee's total weight depends on both GSM and how much fabric the pattern uses:
| Fabric Weight | Approx. Finished Tee Weight (Size M) |
|---|---|
| 140 GSM (lightweight) | 110–130 g |
| 180 GSM (midweight) | 150–170 g |
| 200 GSM (heavyweight) | 180–200 g |
| 220+ GSM (heavy interlock) | 210–240 g |
These figures shift with cut (classic vs. oversized, which uses more fabric per unit) and size — an XXL can run 15–20% heavier than a medium in the same fabric. If you're planning a size run, cross-check against our t-shirt size guide before placing a bulk order.
So What's the Best Fabric Weight for a T-Shirt?
There's no single "best" weight — the right number depends on what the shirt needs to do:
- 4.0–4.5 oz (135–155 GSM): Hot-climate retail, drapey fashion fits, high-volume event giveaways where cost per unit matters most.
- 5.0–5.5 oz (170–190 GSM): The default for most everyday blank tees — balances hand-feel, durability, and price.
- 6.0–6.5 oz (200–220 GSM): Premium streetwear, oversized drops, and brands that want the shirt to feel substantial on its own.
- 7.0+ oz (235+ GSM): Heavy interlock or terry builds for elevated basics and cooler-weather pieces.
Weight also interacts with your decoration method. Heavier, tighter knits generally hold fine screen-print detail and embroidery stitching better than very light jersey, which can pucker. See our screen printing vs. DTG vs. embroidery comparison for how fabric weight affects each method's results.
Why the Same GSM Can Still Feel Different
Two fabrics at an identical GSM can still feel completely different in hand, because weight alone doesn't capture yarn quality or knit structure. A long-staple fiber like Peruvian Pima cotton spins into a finer, smoother, stronger yarn than standard upland cotton, so a 180 GSM Pima tee can feel denser and drape better than a 180 GSM shirt from coarser cotton that just has more bulk packed into the same area. When you're comparing supplier quotes, ask for both the weight and the fiber — weight alone is only half the spec.
Quick Reference: Converting a Supplier Quote
| Supplier Quotes | Convert To Compare | Formula |
|---|---|---|
| 6.1 oz/yd² | GSM | 6.1 × 33.906 = 206.8 GSM |
| 190 GSM | oz/yd² | 190 ÷ 33.906 = 5.6 oz/yd² |
FAQ
Is GSM or ounces more accurate for fabric weight?
Neither — they're the same measurement in different units. The only error risk is comparing an ounce quote to a GSM quote without converting first, which can make two nearly identical fabrics look very different on paper.
How many grams does a standard blank tee weigh?
Most midweight (170–190 GSM) adult medium tees land between 150–170 grams finished. Heavier 200+ GSM styles run 180–200+ grams, and size and cut both shift that number.
What's the best fabric weight for screen printing?
5.0–6.5 oz (170–220 GSM) is the sweet spot for screen printing — heavy enough to hold ink deposits without puckering, light enough to stay comfortable for everyday wear.
Why do some suppliers quote ounces and others GSM?
It's mostly regional convention — U.S.-based mills often use ounces per square yard, while international and especially South American and European mills typically use GSM. Always convert before comparing.
Ready to compare weights in person? Browse our Pima cotton tees across multiple weight options, or see the full blank tees collection.
