GSM to Oz Converter: The Short Answer
A buyer compares two denim quotes, which is the usual reason to reach for a GSM to oz converter. One mill quotes 340 gsm and the other 10 ounces. The GSM to oz converter settles it in one step: 340 grams per square metre is 10.03 ounces per square yard, so the two quotes describe almost the same fabric. The rule behind it is that one ounce per square yard is 33.906 grams per square metre. Multiply ounces by 33.906 to get gsm, and divide gsm by 33.906 to get ounces.
The conversion is exact apart from rounding. What causes errors is not the maths but the unit: a figure quoted in ounces can mean ounces per square yard or ounces per linear yard, and the two are different numbers for the same cloth. The section on linear yards below shows how to catch it.
Use the GSM to Oz Converter
Choose the direction, enter the weight and, if you like, the fabric width in inches. The GSM to oz converter returns the weight in grams per square metre and in ounces per square yard. With a width, it also shows the weight of one linear metre and one linear yard of that fabric, which is what a mill may mean when it quotes a roll in ounces.
GSM to oz converter
GSM and ounces per square yard
Conversion factor 33.906 (1 oz/yd² = 33.906 gsm), rounded for display. Linear yard weight depends on the fabric width you enter.
Type the number from the quote exactly as written, then compare it with the other quote in the same unit. If the two figures are within a few gsm of each other, the difference is rounding. If they are further apart, the fabrics are different weights, and the quotes are not comparable until you resolve it.
GSM to Oz: Common Fabric Weights
The first table converts common gsm values, from light jersey to heavy fleece, into ounces per square yard. These are conversions, not recommendations: use the weight your design needs, and see our guide to fabric GSM for T-shirts and hoodies for what each does for a garment.
GSM converted to ounces per square yard
| GSM | Ounces per square yard |
|---|---|
| 120 | 3.54 |
| 140 | 4.13 |
| 160 | 4.72 |
| 180 | 5.31 |
| 200 | 5.90 |
| 240 | 7.08 |
| 280 | 8.26 |
| 320 | 9.44 |
| 360 | 10.62 |
| 400 | 11.80 |
| 450 | 13.27 |
Calculated as gsm ÷ 33.906 and rounded to two decimal places.
Knit suppliers rarely quote in ounces and denim suppliers rarely quote in gsm, so most conversions cross the divide in one direction. The next section covers the other.
Use the table as a sense check rather than a specification. A 180 gsm jersey is a little over 5 ounces per square yard, and a 320 gsm fleece is about 9.4. If a quote in ounces gives a gsm far from what you expect for the garment, the quote or the unit is probably not what you think it is, and it is cheaper to ask before ordering than after.
Oz to GSM: Denim Weights
Denim is where ounces survive most strongly. The table converts the usual range of denim weights from ounces per square yard to gsm, so you can place a quote in context. Our denim fabric weight guide with an oz to gsm chart explains how each weight is typically used.
Denim ounce weights converted to gsm
| Ounces per square yard | GSM |
|---|---|
| 6 | 203 |
| 8 | 271 |
| 10 | 339 |
| 12 | 407 |
| 14 | 475 |
| 16 | 542 |
Calculated as ounces × 33.906 and rounded to the nearest whole gram.
Denim weights in grams per square metre
GSM
Arithmetic: ounces per square yard × 33.906. Illustrative weights from the table.
Each two-ounce step is about 68 gsm, which is why a 12 ounce denim feels distinctly heavier than a 10 ounce. If your quotes differ by an ounce or less, treat them as similar, and ask for a swatch.
The Linear Yard Trap
Most denim and woven fabrics are quoted in ounces per square yard, but some sellers quote ounces per linear yard, which is the weight of a one-yard length of the whole roll width. The two differ by the fabric width. Multiply the ounces per square yard by the width in inches and divide by 36 to find ounces per linear yard.
A 12 oz/yd² fabric expressed per linear yard at three widths
| Fabric width | Ounces per linear yard |
|---|---|
| 54 in | 18.0 oz |
| 58 in | 19.3 oz |
| 60 in | 20.0 oz |
Calculated as 12 × width in inches ÷ 36. Illustrative widths and weight.
A buyer who reads 20 ounces from a quote as 20 oz/yd² would believe the fabric is far heavier than it is. Whenever a figure looks out of line with the garment, ask which unit it is in. The converter shows both so that you can check.
What the Weight Gap Means for the Buyer
A heavier fabric uses more cloth by weight, so it costs more per metre when priced per kilogram. The pie compares a 14 ounce denim with a 10 ounce denim, to show how much of the heavier cloth is extra weight.
Share of a 14 oz/yd² denim's weight above a 10 oz/yd² denim
- Shared with the 10 oz fabric (339 gsm)71.4%
- Extra weight of the 14 oz fabric (136 gsm)28.6%
Arithmetic: 4 ÷ 14 = 28.6 per cent. 14 oz/yd² is 475 gsm and 10 oz/yd² is 339 gsm. Illustrative weights.
Nearly 29 per cent more cloth by weight is a visible difference in hand, in cost and in how the garment sews. Use the fabric kilograms to metres calculator to see how a weight change alters the length per kilogram.
Why Denim Still Uses Ounces
Ounces per square yard became the habit in denim because mills and brands in the long-established denim trade described their cloth that way, and the habit has stuck. The weight is shorthand for a whole set of properties: how stiff the cloth feels, how it ages, how it sews and what it costs. A GSM to oz converter lets a buyer who thinks in grams talk to a mill that thinks in ounces without either side guessing.
For a brand developing jeans, the practical point is to write both units in the specification and to treat them as one fabric weight, not two. When the mill says 12 oz and your tech pack says 407 gsm, nobody should need to wonder whether the numbers describe the same cloth. Our guide to types of denim fabric describes how weight and construction fit together.
Tolerance and Rounding When You Convert
Fabric weights always carry a tolerance. A mill that quotes 12 ounces will deliver cloth within a range around that figure, and the range converts like the number does. Converting a rounded figure back and forth compounds the rounding, so keep the original value and convert once. A 10 ounce fabric is 339 gsm, but converting 339 gsm back gives 9.998 ounces, which rounds to 10, and nothing is lost.
Where it matters is on a tight specification. If your tolerance is a few per cent, convert with the full factor of 33.906 and keep a decimal place rather than rounding to the nearest ten. The GSM to oz converter above shows one decimal place for gsm for exactly that reason.
How to Use the Converter Well
Convert early with the GSM to oz converter, so that every quote and every specification is in the same unit before you compare. A few steps make it routine.
Working across ounces and grams
- 1Note the unitCheck whether each figure is gsm, oz/yd² or oz per linear yard.
- 2ConvertUse 33.906 to move between gsm and oz/yd².
- 3CompareTreat gaps under a few gsm as rounding.
- 4Check widthConvert linear yard weights using the width.
- 5Write bothPut both units in the specification.
Measured weight is the final check. Weigh a swatch with the GSM calculator and compare the reading with the converted figure. Standards bodies such as ISO and ASTM International publish the test methods that laboratories use.
Questions to Ask a Fabric Supplier
A short list of questions removes ambiguity before an order is placed.
What to confirm about fabric weight
- Is the weight in gsm, ounces per square yard or per linear yard?
- Is it the weight of greige, finished or washed fabric?
- What tolerance applies to the stated weight?
- Is the width full width or usable width?
- Will the bulk match the weight of the approved sample?
- Can the weight appear in both units on the order?
A general checklist. Your supplier confirms what applies to the fabric.
Denim weight interacts with fit, wash and cost, which our guide to types of denim fabric and the guide to the cost of manufacturing jeans explore.
How Ruhrose Helps You Specify Fabric Weight
Ruhrose develops hoodies, fleece, jersey, denim and woven casualwear for UK buyers, with production in Bangladesh. We write fabric weights in both gsm and ounces where denim is involved, so that quotes and samples refer to the same cloth, and we sample before bulk. Ruhrose's clothing manufacturing pages show what we make.
Before you compare two fabric quotes, ask yourself one question: are they in the same unit?