Around the world, a "medium" or a "size 12" means something different at nearly every brand. Buying online without trying things on turns that into returns, postage and wasted time. A size chart solves most of the problem, but only if you know what it's measuring and how to compare it with your own numbers.
Step 1: Take your measurements once, properly
Use a soft tape measure, wear light clothing and stand relaxed. Keep the tape level and snug but not tight.
- Bust or chest: around the fullest part, under the arms.
- Waist: at the narrowest point, usually just above the navel.
- Hips: around the fullest part of the hips and seat.
- Inseam: from the crotch to the ankle bone, easiest measured on a pair of trousers that fit well.
- Shoulders: across the back from one shoulder point to the other, useful for jackets and shirts.
Write the numbers down in both centimetres and inches, because brands use different units, and update them every few months.
Step 2: Check what the chart is measuring
Size charts come in two kinds, and confusing them is the most common mistake:
- Body measurements: "fits a waist of 76–80 cm". Compare directly with your own numbers.
- Garment measurements: "waist: 82 cm", measured flat across the item and doubled. These include ease, the extra room that lets you move. A garment measurement a few centimetres larger than your body is normal.
If the chart doesn't say which it is, look for a "how to measure" note or ask customer service.
Step 3: When your measurements fall in different sizes
Most people don't fit neatly into one row. Your hips might match a 14 while your waist matches a 12. Your body shape tells you which number to prioritise:
- For fitted trousers and skirts, go with the hip measurement if your hips are fuller, then take in the waist.
- For dresses and tops, prioritise the bust or chest, since it's harder to alter.
- For stretch fabrics, you can usually size to the smaller number.
If you're not sure how your measurements compare, a tool like https://www.bodyshapecalculator.org/ takes your bust, waist and hip figures and suggests a likely body shape with the ratios behind it, which makes it easier to predict where a garment will be tight or loose.
Step 4: Read beyond the chart
- Fit description: "slim fit", "relaxed" and "oversized" change how the same size feels.
- Fabric content: 2–5% elastane adds stretch; 100% cotton or linen doesn't give.
- Model details: "Model is 175 cm and wears size S" is a helpful reference point.
- Reviews: look for comments like "runs small" from people who give their usual size.
International size conversions
UK, US, EU and Asian sizing systems don't convert neatly, and brands don't always follow them. A UK 12 is often listed as a US 8 and an EU 40, but always use the brand's own chart rather than a generic table. There's a good overview of why sizing systems differ in the clothing sizes article.
When two charts disagree
If the same measurements put you in a medium on one site and a large on another, trust the brand chart for the specific item, not the one you used last time. Then read the reviews: comments such as "runs small in the hips" tell you which way to adjust.
Checklist before you click "buy"
- Compare your measurements with the brand's own chart.
- Check whether it shows body or garment measurements.
- If you're between sizes, prioritise the measurement that's hardest to alter.
- Read the fit description, fabric and reviews.
- Check the returns policy, just in case.
A few minutes with a tape measure saves a lot of trips to the post office.