What is Stretch?

Why do fabrics stretch?

Stretch fabrics (knit fabrics) are made using interlaced looped fibres rather than woven fibres. The 'knit' or loops give the fabric some of its stretch, alongside elastic fibres which have stretchy properties themselves; for example lycra/spandex/elastane (three names for the same fibre), rayon/viscose (two names for the same fibre) or polyester.

Woven and knit fabrics

What is stretch and how is it calculated?

The stretch of fabrics is expressed either as '2-way' or '4-way'. 2-way stretch is horizontal, running across the fabric from selvedge to selvedge. 4-way stretch is both horizontal AND vertical, running across the fabric and up/down the fabric.

2-way stretch

4-way stretch

Stretch is expressed as a percentage and is quite simply calculated –

Stretched fabric width - Original fabric width

----------------------------------------------------------- x 100 = Stretch percentage

Original fabric width

For example: If you have a 10cm square piece of fabric, stretch it across it’s width until you feel resistance. This fabric stretches to 15cm so the horizontal stretch is 50% (15 - 10 = 5, divided by 10 = 0.5, multiplied by 100 = 50%).

Measure fabric before stretching

Stretch in knit fabric

Now repeat this process from top to bottom of the fabric. This piece of fabric stretches to 13cm, so the vertical stretch is 30% (13 - 10 = 3, divided by 10 = 0.3, multiplied by 100 = 30%).

Measuring top-bottom stretch

So this fabric has 4-way stretch, written as 50%/30%. If there is no vertical stretch then the fabric has 2-way stretch, written as 50%. Simple!

What can I use different stretch fabrics for?

Knit fabrics can vary greatly in stretch, even within a specific category of knit fabric, but in general the following is a good guide:

Type of Fabric	Type of Stretch	Typical Stretch	Used for
Cotton Jersey	2-way or 4-way	30%	Dresses, Skirts, Tops, Pyjamas, Shorts
Cotton Lycra	4-way	60%/40%	Dresses, Pencil Skirts, Leggings, Baby Clothes, Tops, Pyjamas
Lycra	4-way	70%/40%	Swimwear, Sportswear
Ponte De Roma	2-way	55%	Dresses, Skirts, Jackets, Cardigans
Hacci Sweater	2-way	45%	Cardigans, Jumpers, Dresses
French Terry	2-way	55%	Cardigans, Jumpers, Dresses
Sweatshirt Fleece	2-way	10%	Sweaters, Hoodies

The type of fabric you use for your project will depend on the requirements of the garment. Your pattern will normally specify which types of fabric you can use and any required stretch. As you get more confident sewing with stretch fabrics you can also use them for patterns designed for woven fabrics. Take a look at the following articles for some great hints and tips for converting patterns from woven to stretch fabric:

https://www.seamwork.com/issues/2016/02/from-woven-to-knit

http://houseofpinheiro.com/2015/09/merchant-and-mills-bantam-tips-for-sewing-with-jersey-on-woven-patterns.html

For tighter fitting clothes like leggings/sportswear, 4-way stretch is essential as the fabric will need to stretch both ways (e.g. around the legs and up and down the knee joint).

For looser fitting items or for fitted items which don’t need to give, 2-way stretch will usually suffice, but you can still use 4-way stretch fabrics.

The advantage of 4-way stretch is that you can use the stretch/pattern in either direction. 2-way stretch will offer more stability for fitted clothing, similar to a woven fabric, but will also give you some room to breathe!

For more information about knit fabrics, plus hints, tips and tutorials for sewing with them, see the Girl Charlee Pinterest page