Two fabrics can both be called “15 oz canvas” and still perform very differently. One may be tightly woven from strong two-ply yarn; the other may be loosely woven with a heavy finish adding weight. The only way to compare offers fairly is to read, and write, a proper fabric specification. This guide explains each term you will meet on a specification sheet for industrial fabrics such as canvas, drill and sheeting.

Fabric Weight: GSM and Ounces

GSM (grams per square metre) is the weight of one square metre of fabric. It is the most widely used measure in India for drill, sheeting and apparel fabrics.

Ounces (oz) are traditional in the canvas trade. In most specifications, oz means ounces per square yard. Because a square yard is smaller than a square metre, the conversion is:

GSM = oz per sq yd x 33.9

Canvas weight (oz/sq yd)	Approximate GSM	Typical uses
7 oz	237	Oilskin jackets, light bags
8 oz	271	Light tents, rainwear, linings
10 oz	339	Bags, tents, boat and animal covers
12 oz	407	Tents, heavier bags, covers
15 oz	509	Tarpaulins, heavy tents, covers
18 oz	610	Truck covers, heavy-duty tarpaulins
24 oz	814	Extra heavy-duty waxed covers

Two cautions. First, some traders quote ounces per linear yard of a specific width, which gives a different number, so always confirm the basis. Second, check whether the weight is measured before or after finishing; wax and other treatments add weight without adding strength.

Yarn Count

Yarn count describes how thick a yarn is. Cotton yarn in India is usually given in the English cotton count (Ne): the higher the number, the finer the yarn. A 10s yarn is thick and strong, typical of heavy canvas; a 40s yarn is fine, typical of shirting and lighter sheeting.

Ply matters too. “2/10s” means two 10s yarns twisted together. Plied yarns are stronger, more even and more abrasion resistant than a single yarn of similar weight, which is why heavy cotton canvas for tents and tarpaulins is often woven from plied yarns.

Construction: Ends and Picks

Construction tells you how densely the fabric is woven:

• Ends per inch (EPI): the number of warp threads (running lengthwise) in one inch.
• Picks per inch (PPI): the number of weft threads (running across) in one inch.

A specification such as 20 x 20 / 60 x 60 reads as: warp count 20s, weft count 20s, 60 ends per inch and 60 picks per inch. This is one of the most common qualities of sheeting cloth and muslin cloth. Higher ends and picks generally mean a tighter, stronger, more water-resistant fabric, as long as the yarn count is suitable.

Weave Type

• Plain weave: each weft passes over one warp and under the next. Firm, stable and the standard for canvas.
• Twill and drill: a diagonal rib pattern that packs more yarn into the fabric, giving density, drape and abrasion resistance. Used for uniforms and workwear. See our twill and drill cloth.
• RIB STOP: a plain or twill base with stronger reinforcing yarns woven in at regular intervals, forming a grid. If the fabric is cut, the tear tends to stop at the next reinforcing line. Popular for tents, covers and animal rugs.
• Duck and panama (basket) weaves: variations of plain weave using paired yarns for extra weight and strength.

Width

Width is the usable width of the fabric, usually in inches. Industrial canvas is commonly woven from 36 to 84 inches wide, and drill and sheeting from 50 to 63 inches. Choosing a width that fits your pattern pieces or panel sizes reduces joints and wastage, which in tarpaulins and tents also reduces the number of seams where water can enter.

Fibre Content

State the fibre and blend ratio clearly: 100% cotton, polyester-cotton (for example 65/35 or 50/50), 100% polyester or recycled PET fabric. Fibre content affects strength, shrinkage, how dyes and finishes behave and how the fabric ages in sun. Our article on cotton canvas vs polyester cotton canvas compares the two most common choices.

Finishes and Treatments

Finishes are where most of the functional performance of industrial fabric comes from. List each one you need:

• Water repellent or wax proofing
• Flame retardant, durable or non-durable
• Rot-proof, anti-mildew and anti-bacterial
• UV resistance
• Pre-shrinking
• Colour, with dye class and fastness requirements, for example vat-dyed olive for dyed canvas

Performance Values

For technical buyers, weight and construction are not enough. Ask for tested values such as tensile strength (warp and weft), tear strength, water resistance (spray rating or hydrostatic head), shrinkage percentage and colour fastness to light, washing and rubbing. These numbers tell you how the fabric will actually perform.

A Sample Specification

Here is how a clear specification for a tent fabric might read:

100% cotton canvas, 2/10s x 2/10s, plain weave, 15 oz per sq yd (about 509 GSM) finished, 72 inch width, vat-dyed olive green, durable water repellent, rot-proof and flame retardant finish, shrinkage below an agreed percentage, tensile and tear strength to the buyer’s stated values.

With a specification like this, every supplier quotes on the same fabric, and the goods you receive can be checked against it.

Buyer’s Checklist

1. Fibre and blend ratio
2. Yarn count and ply (warp and weft)
3. Construction (ends and picks per inch)
4. Weave (plain, twill, RIB STOP)
5. Weight, with the unit and whether greige or finished
6. Width
7. Colour and dye class
8. Finishes and treatments
9. Performance values and test methods
10. Tolerances, roll length and packing

Frequently Asked Questions

How do I convert oz to GSM?

Multiply ounces per square yard by about 33.9. For example, 10 oz canvas is roughly 339 GSM and 15 oz canvas is roughly 509 GSM.

What does 20×20 / 60×60 mean in fabric?

It means the warp and weft yarns are both 20s count, and there are 60 warp threads (ends) and 60 weft threads (picks) per inch.

Is a higher GSM fabric always stronger?

Not always. Strength depends on yarn quality, ply, construction and weave as well as weight. Finishes such as wax also add weight without adding strength, so ask for tensile and tear values.

What is RIB STOP fabric?

RIB STOP fabric has stronger reinforcing yarns woven in at regular intervals in a grid pattern. If the fabric tears, the tear tends to stop at the next reinforcing line.

Why is fabric width important?

The right width reduces joints and wastage when cutting panels for tents, tarpaulins and garments. Fewer seams also mean fewer weak points and fewer places for water to enter.

Talk to A K Industrial Fabrics

A K Industrial Fabrics Private Limited has manufactured and supplied industrial and technical fabrics since 1983, with in-house pre-treatment for water, weather and flame resistance. Browse all our fabric products, see the industries and applications we serve, or send your specification through our contact page and our team will recommend the right construction and finish.