What decides whether a knit is heavy or light
Short answer: Weight comes from the thickness of the yarn, the density of the stitches and whether there is an extra thread in the structure. These are three choices, and they can be combined freely. That is why two fabrics of the same weight can feel completely different.
The yarn is the first choice
A coarse yarn puts more material into each stitch. Twice as thick a yarn gives almost twice as heavy a fabric at the same density. The thickness of the yarn is therefore the first thing that decides how heavy a fabric becomes, and you often feel it with your fingers before you judge anything else.
Density is the second
More stitches per centimetre mean more yarn per surface. A dense knit can be heavy even with a fine yarn. Conversely, a coarse yarn in an open stitch can be fairly light. Density and yarn have to be read together. See bamboo jogging suit for men.
The structure is the third
Sweatshirt fabric and terry have an extra thread that forms loops. That thread counts towards the weight without the fabric necessarily becoming thicker. The structure can therefore add weight in a way you cannot see from outside. See bamboo loungewear for men and bamboo footies for men.
Weight in grams per square metre
Weight is often given in grams per square metre, so fabrics can be compared regardless of garment size. Under one hundred and fifty grams counts as light in jersey. The figure is a guide and not a verdict, since it does not say how the fabric feels or how it drapes.
Heavy and light in daily life
A light fabric suits warm weather and layering under other clothes, because it takes up little space and feels airy. A heavy fabric suits better when you want something that drapes calmly and holds warmth. It is more about use than quality, and both have their place.
Terry and sweatshirt fabric
Terry and sweatshirt fabric have loops on the back that make the fabric soft and a little thicker. The loops trap air, which gives a cosy feel. So a sweatshirt fabric can feel heavier than the figure alone suggests, because the loops add bulk and make it more compact in the hand.
Open heavy knit
A heavy knit does not have to be dense. An open, coarse knit can weigh a lot and still let more air through than a dense, light knit. Weight does not say everything about how warm a garment is. Also look at how tight the stitches are and how the fabric is constructed.
How to feel the weight
Take the fabric between your fingers and rub it lightly. If it feels thin and smooth, it is probably light. If it feels full and has some depth, it is heavier. Also hold it in your hand and feel how it drapes. Drape and weight go together, and a heavier fabric often hangs more calmly.
Choose by purpose
Think about what the garment will be used for. If it is to be a layer close to the body, a light fabric suits. If it is to be the cosy garment at home, a heavier one suits. Weight is a tool that helps you choose, and not a goal in itself.
Frequently asked questions
What is a light fabric in grams
Under one hundred and fifty grams per square metre counts as light in jersey. The limit is a guide, and a fabric just above it can still feel light, depending on yarn and structure.
Is heavy fabric always warmer
Often, but an open heavy knit can let more air through than a dense light knit. Weight, density and structure together decide how warm the fabric feels in practice.
Why do two fabrics of the same weight feel different
Because the weight can come from yarn, density or structure in different mixes. Two fabrics can weigh the same and still have a completely different feel, drape and airiness.
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