What is a Bias Cut?

A bias cut is a garment construction technique where fabric is cut diagonally across the grain, typically at a 45-degree angle to the lengthwise and crosswise threads. Cutting fabric on the bias gives woven fabric greater flexibility and allows it to drape and follow the contours of the body more fluidly than the same fabric cut on the straight grain.

Bias cutting is particularly associated with flowing dresses, skirts and evening wear, but the technique can also be used for individual garment pieces, trims and bindings.

What does "cut on the bias" mean?

To understand bias cutting, it helps to understand the grain of fabric.

In a woven fabric, threads run in two main directions.

The Warp (lengthwise grain) runs parallel to the selvage, the finished edge running along the length of the fabric.

The Weft (crosswise grain) runs from selvage to selvage, at approximately 90 degrees to the lengthwise grain.

The true bias runs diagonally across these threads at approximately 45 degrees.

When a pattern piece is positioned along this diagonal rather than following the straight grain, it is described as being cut on the bias.

Why does bias-cut fabric behave differently?

A woven fabric generally has relatively little natural stretch along its lengthwise grain and somewhat more across its width.

But pull it diagonally and something interesting happens.

The woven threads can shift slightly in relation to one another, giving the fabric considerably more give and flexibility.

Importantly, the fibres themselves haven't suddenly become stretchy. Instead, it's the structure of the weave moving on the diagonal that creates the additional give.

This allows bias-cut fabric to drape, move and mould around curves in a way that the same fabric may not when cut on the straight grain.

Does bias-cut fabric stretch?

Yes, but it's different from the stretch you get from elastane or a knitted fabric.

Bias stretch is created by the way the woven threads move relative to each other when pulled diagonally.

This gives a bias-cut garment a form of mechanical stretch or give, even when the fabric contains no elastic fibre such as elastane. However, this shouldn't be confused with modern fabrics specifically engineered and marketed as mechanical stretch, which can provide stretch regardless of the direction in which the garment pieces are cut.

How much give you get depends on the fabric. A soft, loosely woven textile may respond dramatically to bias cutting, while a stiff or tightly woven fabric may show considerably less movement.

Is bias cut the same as mechanical stretch?

Not exactly, although the two concepts are related.

Mechanical stretch describes stretch or flexibility created without adding an elastic fibre such as elastane or spandex.

When woven fabric is cut on the bias, the diagonal orientation allows the warp and weft threads to move slightly in relation to one another. This creates additional mechanical give even though the fibres themselves aren't elastic.

However, not all fabrics described as having mechanical stretch are bias cut.

In modern uniforms and workwear, mechanical stretch fabrics are often specifically engineered through their yarn or fabric construction to provide greater freedom of movement. The garment can therefore have stretch while its pattern pieces are still cut on the regular grain.

This is why you may see uniform garments advertised as:

• Mechanical stretch – stretch created through the construction of the fabric rather than an added stretch fibre.
• 2-way stretch – the fabric stretches primarily in one direction.
• 4-way stretch – the fabric stretches in both directions.
• Elastane stretch – an elastic fibre such as elastane has been incorporated into the fabric.

A bias cut and mechanical stretch can therefore produce a similar effect, greater flexibility and freedom of movement without necessarily adding elastane, but they aren't the same construction technique.

What does a bias-cut garment look like?

Bias-cut garments are particularly known for their fluid drape.

Rather than holding a rigid shape away from the body, the fabric can fall softly and follow the body's contours.

This is why bias cutting is so strongly associated with:

• slip dresses
• evening dresses
• skirts
• camisoles
• lingerie
• flowing tops
• formalwear

Silk, satin and other fluid fabrics can produce especially distinctive results when cut on the bias.

Bias cut vs straight grain

The same fabric can behave surprisingly differently depending on how the pattern pieces are positioned.

Straight-grain cut: generally provides greater stability and helps the garment retain its intended structure.

Bias cut: provides more give, movement and fluidity and allows the fabric to conform more closely to curves.

Neither method is inherently better.

A structured corporate shirt needs stability, while a flowing evening dress might benefit from exactly the movement a bias cut provides.

The construction technique needs to suit the garment.

Does bias cut mean form fitting?

Not necessarily.

Bias cutting is often used in garments that skim or follow the body because of its natural drape, but a garment doesn't have to be tight or form fitting to be bias cut.

A loose skirt or flowing dress can also be cut on the bias simply to take advantage of the movement and drape it creates.

What is bias binding?

Bias cutting isn't only used to make entire garments.

Narrow strips of fabric can be cut on the bias to create bias binding or bias tape.

Because the strips have additional flexibility, they can bend smoothly around curved fabric edges such as:

• necklines
• armholes
• curved hems
• pockets
• decorative edges

If those strips were cut entirely on the straight grain, they would be much more difficult to manipulate around curves without puckering.

Bias binding is therefore a great example of bias cutting being used for a practical construction purpose rather than simply to change the silhouette of a garment.

Why is bias cutting more difficult?

Bias-cut fabric can be rather less cooperative than straight-grain fabric.

That lovely flexibility also means pieces can stretch, distort or shift during cutting and sewing.

Bias-cut garments may also change slightly in length after they're assembled because gravity can cause sections of the fabric to relax and stretch.

For this reason, dressmakers sometimes allow a bias-cut garment to hang before finishing the hem so the fabric has time to settle.

Accurate cutting and careful handling are particularly important.

Who made bias-cut clothing famous?

Bias-cut clothing became particularly influential in women's fashion during the 1920s and 1930s.

French designer Madeleine Vionnet is especially associated with developing and popularising sophisticated bias-cut techniques.

Rather than forcing fabric into shape using extensive structure, Vionnet explored how fabric could naturally drape around the body when positioned on the diagonal.

Her work helped establish bias cutting as one of the defining construction techniques of 20th-century fashion.

Is bias cutting common in uniforms?

Full bias-cut garments are considerably less common in everyday uniforms and workwear than they are in fashion and formalwear.

Most uniform garments benefit from stability, predictable sizing and durability, so their major pattern pieces are generally positioned according to the straight grain.

However, bias-cut components certainly appear in garment construction, particularly bias binding and other finishing details.

Understanding grain direction is also useful when comparing garment construction because how fabric is cut can have a significant effect on how it hangs, moves and retains its shape.