Suit Fabric and Construction Guide

Wool: the usual starting point

Wool is the cloth most suits are made from, and for good reason. It holds its shape after a day of wearing, drapes in a clean line from shoulder to hem, and recovers from creases better than cotton or linen. A smooth worsted wool in a dark plain colour is the usual choice for formal suits, because it matches its trousers neatly and suits formal settings. Wool also breathes, so it works across more of the year than a heavy cotton or a light linen.

Wool weight changes how the suit feels. A heavier wool holds a firmer shape and shows a tight fit clearly, while a lighter wool drapes more softly and forgives a little looseness. Wool with a little stretch added gives a little when you move, which can make a fitted size feel more comfortable, but it will not turn a size that is too small into one that fits.

Cotton, linen and warm weather cloths

Cotton suits are softer and more casual than wool suits, with a matte surface and a relaxed drape. They crease more readily than wool, so a cotton suit will show the marks of a day of sitting and moving, and the fit needs a little more ease to look relaxed rather than strained. Cotton is a good choice for warm weather and casual settings, but it is less suited to formal occasions where a smooth wool reads better.

Linen is lighter still, and it breathes well in heat, but it creases more than any other suit cloth, and the creases are part of its look. A linen suit is usually cut with a relaxed fit and a soft shoulder, because a close fit in linen will show every pull and crease. Linen blends, with wool or cotton mixed in, keep some of the breathability while creasing less, and they are a practical middle ground for warm weather.

Blends and stretch

Blends mix fibres to balance their strengths, and the most common suit blend is wool with a small amount of stretch fibre. The stretch gives the jacket and trousers a little give when you sit, walk or reach, which makes a fitted size feel more comfortable and a regular size feel more forgiving. A blend with more stretch will feel closer in the same size than a firm wool with no stretch, so read the fabric note before you pick between two sizes.

Other blends mix wool with cotton, linen or silk for a different surface. A wool and silk blend has a soft sheen and a smooth drape, while a wool and linen blend is lighter and more textured. These blends change the look more than the size, but a softer cloth drapes loosely and a firmer cloth holds its line, so judge the size by the fit and the blend by the look and the season.

Canvas, fusing and how a jacket holds its shape

Inside the front of a jacket, makers use either a canvas layer or a fused layer to give the chest its shape. A canvas layer is a piece of cloth sewn into the jacket, and it moves with your body, shaping itself to you over time and letting the jacket breathe. A canvassed jacket feels softer and more alive, and it usually costs more, because the work is done by hand or by a slower process.

A fused layer is a stiffening layer glued to the cloth, and it gives a firmer, flatter front at a lower cost. It holds its shape well when new, but it can bubble or stiffen with heat and cleaning over time. For sizing, a canvassed jacket will settle and soften with wear, while a fused jacket will hold the shape it was bought in. Neither changes the size letter, but the canvas will feel more forgiving as it settles.

Lining and breathability

The lining is the smooth cloth inside the jacket, and it decides how the jacket slides on over a shirt and how it breathes. A fully lined jacket has lining throughout, which makes it easy to put on and take off and gives a smooth finish inside, but it is warmer. A half lined jacket has lining only in the sleeves and the upper back, which makes it cooler and lighter, and it is a common choice for warm weather suits.

Lining also affects the fit, because a lined jacket has an extra layer that takes up a little room, while an unlined jacket sits closer to the body. The difference is small, usually a fraction of an inch as a rough guide, but it can matter when you fall between sizes, and a half lined jacket will feel cooler and lighter in heat.

How fabric changes the size you pick

• Firm wool with no stretch: pick the size your measurements point to, and size up when between sizes, because the cloth will not forgive a tight fit.
• Stretch blend: the smaller size can work when the shoulders fit, because the stretch gives back a little room.
• Cotton or linen: allow a little more ease, because these cloths crease and show a tight fit clearly.
• Canvassed jacket: expect it to settle and soften with wear, so a close fit on the first wear may ease slightly.
• Half lined or unlined jacket: expect a cooler, lighter feel, and check the fit without the extra lining layer in mind.