To wash a sweater (jumper) without shrinking it, follow the care label, then hand-wash it in cool water or use the wool or delicate cycle at cold or 30°C with a gentle detergent, and avoid hot water, heavy agitation and the tumble dryer. To stop it stretching, never wring or hang it wet: press the water out by rolling it in a towel, then dry it flat on a towel or rack, easing it back to its original shape.
Key takeaways
- Heat and agitation together cause most wool shrinkage, so keep water cool and handling gentle.
- Hand washing is the safest option, but a wool or delicate machine cycle works for many knits.
- Water makes knits heavy, which is why hanging a wet sweater stretches it.
- Roll the sweater in a towel to remove water, then dry it flat and reshape it.
- Measure a favourite jumper before washing so you can reshape it accurately.
Why do sweaters shrink or stretch in the wash?
Wool and other animal fibres have tiny scales on their surface. With warm water, soap and plenty of movement, those scales catch on each other and the fibres lock together more tightly. This is called felting, and it is the reason a wool jumper (sweater) can come out of a hot wash smaller and thicker. Once felting has gone far, it is very hard to undo.
Cotton knits shrink in a different way. Yarns that were stretched during manufacture can relax in warm water and heat, pulling the garment in. Many synthetic knits, such as acrylic, shrink less but can stretch or lose their softness with heat.
Stretching is the opposite problem. A wet knit holds a lot of water and becomes heavy. If you hang it, wring it or lift it by the shoulders, that weight pulls the loops of the knit out of shape, and they can dry that way.
Should you hand-wash or machine-wash a sweater?
Start with the care label. A hand-wash symbol, a “dry clean only” note or a crossed-out tub tells you most of what you need. Where the label allows either method, this table can help you choose.
| Knit | Usual safest method | Notes |
|---|---|---|
| Wool or lambswool | Hand wash, or a machine wool cycle if the label allows it | Cool water and minimal movement prevent felting |
| Cashmere or merino | Hand wash | Fine fibres felt and stretch easily |
| Cotton | Gentle machine cycle, cool water | Avoid high heat and the dryer |
| Acrylic or polyester blend | Gentle machine cycle | Heat can make it limp or stretched |
| Chunky, loose or hand-knitted | Hand wash | Heavy when wet and stretches easily |
Before you wash: measure and prepare
A quick measurement makes reshaping much easier. Lay the jumper flat and note the width across the chest, the length from shoulder to hem and the sleeve length. A tape measure is ideal, and our guide to measuring clothes and yourself shows where to place it.
- Empty the pockets and close any zips or buttons.
- Turn the sweater inside out to protect the outer surface.
- Treat small marks by dabbing on a little of your wool or gentle detergent and leaving it for a few minutes.
How to hand-wash a sweater step by step
- Fill a clean basin or sink with cool or lukewarm water. It should feel cool to slightly warm on your wrist, never hot.
- Stir in a small amount of gentle detergent, ideally one made for wool or delicates. Mix it in before the sweater goes in.
- Submerge the sweater and press it down gently so it soaks through.
- Leave it to soak for 10 to 15 minutes, or as long as the detergent label suggests.
- Squeeze the suds through the fabric with soft pressing movements. Do not rub, twist or scrub.
- Drain and rinse in water at the same temperature. A sudden change from warm to cold can encourage felting in wool. Repeat until the water runs clear.
- Press out the water by pushing the sweater against the side of the basin. Support its full weight with both hands when you lift it.
How to machine-wash a sweater safely
- Check that the label allows machine washing.
- Turn the sweater inside out and put it in a mesh laundry bag.
- Wash it with a few similar, light items, not towels or jeans.
- Choose the wool, delicate or hand-wash cycle at cold or 30°C, or the label temperature if lower.
- Use a gentle detergent in the amount shown, without fabric softener unless the label suggests it.
- Pick the lowest spin speed available.
- Take the sweater out promptly so it does not sit creased and wet in the drum.
How do you dry a sweater flat so it keeps its shape?
Drying is where most stretching happens, and it is also where you can correct small changes in size.
- Lay a large, dry towel flat and place the sweater on top.
- Roll the towel up from one end with the sweater inside, like a Swiss roll.
- Press down on the roll or kneel on it gently to push water into the towel. Do not twist.
- Unroll and move the sweater to a fresh, dry towel or a flat mesh drying rack.
- Reshape it with your hands. Ease the body and sleeves back to the measurements you took, straighten the ribbing and line up the seams.
- Leave it to dry away from direct heat and strong sun. Turn it over after several hours so both sides dry evenly.
Thick knits can take a day or longer to dry fully. If the towel underneath becomes soaked, swap it for a dry one.
Can you hang a sweater to dry?
Not while it is wet. Hanging lets the water weight pull the shoulders and hem downwards. Once it is almost dry, some people drape a jumper over the middle bar of a drying rack, folded in half across the chest, to finish off.
What to avoid when washing knitwear
- Hot water, which encourages felting in wool and shrinking in cotton.
- The tumble dryer, unless the label says it is safe. Heat and tumbling together are hard on almost any knit.
- Wringing or twisting, which stretches and distorts the stitches.
- Radiators and heaters for drying, which can shrink or stiffen fibres.
- Biological detergents on wool or cashmere, as some enzymes are designed to break down protein, and these fibres are protein.
Storing sweaters so they stay in shape
Fold knits and store them flat on a shelf or in a drawer, rather than hanging them, which can stretch the shoulders over time. Make sure they are completely dry before putting them away. Clean knits are also less attractive to clothes moths, so washing before storing for summer is a good habit.
If a jumper has already shrunk, there are a few gentle methods worth trying, which we cover in the Journal’s knitwear guides. If you are buying a replacement, checking your size against the women’s dress size converter helps when brands and countries label sizes differently.
FAQs
What temperature should I wash a wool jumper at?
Follow the label. Most wool care labels allow cold or 30°C on a wool or hand-wash setting. If you are unsure, cool water is the safer choice, and keep the rinse at the same temperature as the wash.
Can I use normal detergent on a sweater?
For cotton and synthetic knits, a mild everyday liquid usually works. For wool and cashmere, a gentle detergent made for wool or delicates is kinder, as some standard products contain enzymes that can damage protein fibres.
How often should I wash a sweater?
Less often than you might think. Wool in particular can go several wears between washes, especially with a T-shirt underneath. Airing it overnight and spot cleaning small marks reduces how often it needs a full wash.
Why did my sweater get longer after washing?
It was probably hung or lifted while wet, so the weight of the water pulled it down. Rewet it, press out the water in a towel and dry it flat, gently pushing it back to its original length.
Is it safe to wash cashmere at home?
Many cashmere care labels allow careful hand washing in cool water with a gentle detergent. If the label says dry clean only, it is safer to follow that, especially for structured or embellished pieces.