Sizing & fit: how to choose the right size

How to measure yourself (or a shirt that already fits) and compare it with a size chart — plain, practical UK advice.

Size labels aren't standard: one brand's medium can be another brand's large. The surest way to get the right fit is to compare measurements, not letters.

The easiest method: measure a shirt that already fits

1. Lay a T-shirt you like flat on a table and smooth it out.
2. Measure straight across the chest from armpit seam to armpit seam. Double it to get the chest measurement of the garment.
3. Measure the length from the highest point of the shoulder, next to the collar, straight down to the hem.
4. Compare these numbers with the size chart on the listing. Check whether the chart gives garment measurements (the shirt itself) or body measurements (the person) — they're different, and the chart should say which.

Measuring yourself

• Chest: put a soft tape measure around the fullest part of your chest, under your arms, keeping it level and snug but not tight.
• Waist: measure around your natural waist, usually just above the belly button.
• Write the numbers down in both centimetres and inches — many listings on Amazon.co.uk use inches.
• A T-shirt needs to be larger than your body measurement so it isn't tight. If the chart gives garment sizes, pick the one that is comfortably bigger than your chest measurement.

Men's, women's and unisex cuts

Listings are usually labelled as men's, women's or unisex. Unisex shirts are often cut like a classic men's T-shirt, while women's styles are often more fitted. If you prefer a relaxed fit in a women's style, consider going up a size — and always check the chart.

Children's sizes

Children's shirts are usually sized by age, but children grow at different rates and brands vary. Measure the child's chest, or a shirt that fits them now, and compare with the chart. If they're between sizes, the bigger one will last longer.

Hoodies and sweatshirts

Hoodies are designed to be worn over other clothes, so they're often roomier. Check the length and sleeve measurements too if you have long arms.

Before you order

• Read the listing's size chart and any notes about fit.
• Check the returns information on the listing in case you need to swap a size.
• If you're buying for a group, collect everyone's sizes in writing — see our guide to ordering matching shirts.

This is general advice. Always follow the size information given by the seller of the shirt you choose.

Last updated 4 October 2026.