How to choose knitted-fabric weight for a finished product

Grammage is the mass per unit of area, usually expressed in grams per square metre (g/m²). It is not the same as the mass of a running metre: at the same grammage, a metre of 180 cm-wide fabric has more area and weighs more than a metre of 150 cm-wide fabric. In B2B purchasing, check whether price and yield are quoted per kilogram, running metre or square metre.

Higher grammage does not automatically mean greater thickness, warmth or quality. Yarn volume, stitch construction, density and finishing affect the feel. A brushed knit may feel fuller without a proportional increase in mass, while a dense knit can be heavy but relatively flat. Judge the material against the function of the garment and the consistency required between batches.

These ranges are for discussion and sampling, not universal standards. A fabric outside them may still meet the brief if its construction, composition and finish are suitable.

• T-shirt: about 140–220 g/m²; compare 100% cotton or elastane-blend single jersey. Check opacity, twist, hand, print and drape.
• Pyjamas: about 120–200 g/m²; compare single jersey or lightweight interlock. Check softness, thermal comfort, seams and shrinkage.
• Sweatshirt: about 240–360 g/m²; compare loopback and brushed sweatshirt fabric. Check shape, reverse, hood, rib and insulation.
• Joggers: about 250–360 g/m²; compare 100% cotton or elastane-blend sweatshirt fabric. Check knee recovery, pockets and seams.
• Leggings: about 250–300 g/m²; compare jersey or sweatshirt fabric with elastane. Check opacity under stretch, recovery and stabilisation.

For a light T-shirt, a lower weight may drape comfortably but can show through in pale colours. A fuller jersey may build more shape and opacity, while adding garment weight. Assess the actual colour and print: a large ink layer or a finish can change the hand.

Nightwear should balance softness, breathability and thermal comfort; a lightweight single jersey and a denser interlock can feel quite different. For sweatshirts, the hood, pockets, seams and rib add weight. For leggings, the key check is opacity when stretched—not the number alone.

A theoretical estimate for the mass of one running metre is: weight per running metre [kg] = grammage [g/m²] × width [m] ÷ 1,000. For example, 200 g/m² at 1.80 m wide is about 0.36 kg per running metre; one kilogram is therefore about 2.78 running metres.

This is only an estimate. The actual result depends on batch weight and width, the measurement method, usable width, pattern layout, print repeat, defects, process allowances and shrinkage. A wider fabric can improve marker efficiency, but the benefit depends on the garment pattern.

Dyeing, washing, stabilisation, softening and brushing can change dimensions, moisture, hand and the measured weight. State whether the specification applies before or after finishing, and agree an acceptable tolerance. For production, the delivered-to-cutting parameter and the finished garment's behaviour under its care instructions are the useful references.

Record construction, composition, supplier, declared and measured weight, total and usable width, hand, opacity, stretch and recovery, dimensions before and after washing, print/finish results, marker yield and sewing-room feedback. Use the same test and photo conditions for each sample.

Include the garment and sketch, season and use, fit and expected shape, preferred fibre blend and stretch, target weight or reference swatch, colour and decoration, care requirements, size range, planned volume, any certificate requirements and sample/production timing. If you do not know the reference weight, send a finished garment or swatch for comparison.

There is no single “best” weight and a heavier fabric is not necessarily more durable. Durability also depends on yarn, construction, density, abrasion and pilling performance, sewing and care. A prototype remains the most reliable way to assess drape, opacity, seams, rib and real garment weight before approving a new style.