How to pick the right size

1. Measure yourself (or a jumper you love)

The single most useful number is your chest measurement. Wrap a soft tape measure around the fullest part of your chest, under the arms, keeping it level and snug but not tight. Write it down in both centimetres and inches, because charts use either.

Even better: take a jumper that already fits you the way you like, lay it flat, and measure straight across from armpit to armpit. Double that figure and you have the garment's chest width, which you can compare directly with the numbers on a size chart. Measure the length from the top of the shoulder to the hem and the sleeve from shoulder seam to cuff while you are there.

2. Read the seller's size chart, not just the letter

An “L” from one brand can be an “M” from another. Many novelty jumpers sold online are made to sizing that runs smaller than typical UK high-street sizes, so always open the size chart on the product page before you choose.

• Check whether the chart shows body measurements (what size person it fits) or garment measurements (the jumper itself). Garment measurements should be a few centimetres bigger than your body for a comfortable fit.
• “Unisex” usually means men's sizing. Women who normally wear a UK 10 to 12 often find a unisex S or M gives a relaxed fit.
• If you're between sizes, size up. A slightly roomy Christmas jumper looks deliberate; a tight one just looks uncomfortable.
• Plan to wear a shirt or thermal underneath? Allow for it.

3. Knit or sweatshirt? How the fabric changes the fit

Knitted jumpers have natural stretch and tend to relax a little with wear. Printed sweatshirts (the all-over photo-print designs) are usually polyester or cotton blends with less give, so the chest and sleeve measurements matter more. Printed “costume” designs, such as fake Santa suits, also look best when they aren't stretched too tightly across the chest.

4. Kids, couples and light-up jumpers

• Children's jumpers are normally sized by age, but height is a better guide. If your child is tall for their age, go up a size; the extra room means it may still fit next December.
• Matching and couples listings can be sold as a single top or as a set. Read the listing carefully and choose a size for each person.
• Light-up jumpers have a small battery pack, usually in an inside pocket. It adds a little bulk, so a snug size can feel tighter than expected.

5. Keep it looking good

Always follow the care label. As a rule of thumb, wash festive jumpers inside out on a cool, gentle cycle, skip the tumble dryer and dry them flat so knits don't stretch. Remove battery packs and any detachable lights before washing, and hand-wash anything with sequins, bells or pompoms.

Ready to choose? Browse all our jumpers.