Quick answer: 1X, 2X, 3X and 4X are US plus sizes, not UK ones. As a rough guide, 1X is about a UK 18–20, 2X a UK 20–22, 3X a UK 22–24 and 4X a UK 24–26. But there is no official standard, and one brand's 2X can be another brand's UK 22–24. Always check the bust, waist and hip measurements on the size chart instead of trusting the letter.
If you have ever ordered a 2X online, waited a week and found it fits like a UK 16 or a UK 26, you are not alone. The X system is one of the most confusing parts of shopping for plus-size clothes in the UK. This guide explains what the numbers mean, gives you a conversion chart, and shows you how to measure yourself so you get it right first time.
What Does the X Mean in Plus Sizes?
The X stands for "extra", as in XL, XXL and so on. In US women's sizing, plus sizes are often written as 1X, 2X, 3X, 4X rather than numbers. The system mainly comes from US and international manufacturers, which is why you see it on many UK online shops that work with global suppliers, including ours.
Each X step covers a range of UK sizes rather than one exact size. That is because X sizes are usually cut with more ease (room) and more stretch than numbered sizes. A 1X top with a little stretch might comfortably fit both a UK 18 and a UK 20.
1X, 2X, 3X, 4X to UK Size Conversion Chart
Below is the body-measurement chart used on the majority of our plus-size pieces. These are body measurements (your measurements), not the flat garment.
| Size | Approx. UK size | Bust (cm) | Waist (cm) | Hips (cm) | Bust (in) |
|---|---|---|---|---|---|
| 1X | 18–20 | 109–117 | 89–97 | 114–122 | 43–46 |
| 2X | 20–22 | 117–124 | 97–104 | 122–130 | 46–49 |
| 3X | 22–24 | 124–132 | 104–112 | 130–137 | 49–52 |
| 4X | 24–26 | 132–140 | 112–119 | 137–145 | 52–55 |
Important: this is a guide, not a rule. Some suppliers cut their 1X as a UK 16–18, and others label 2X as a UK 22–24. The size chart on each product page is always the one to trust. If your measurements fall between two sizes, go by the measurement that matters most for that garment (more on that below).
Our Pink Plus Size Leopard Puff Sleeve Mini Dress comes in 1X–4X.
Is 1X the Same as XXL?
Not quite. XXL (or 2XL) is usually the top of a standard size run, and it is cut on standard-size proportions: a longer, straighter block that is simply scaled up. 1X is the start of a plus size run, which is drafted for a fuller bust, tummy and hips, often with a wider upper arm. In practice, an XXL and a 1X can have similar bust measurements but fit very differently through the arms and hips. If you usually find XXL tight on the arms, try 1X.
Is 1X the Same as 16W or 18W?
US women's sizes (the W sizes) are another US plus-size system. Roughly, 1X covers US 14W–16W, 2X covers 18W–20W, 3X covers 22W–24W and 4X covers 26W–28W. US sizes run about four numbers smaller than UK sizes (a US 14 is about a UK 18), which is how you arrive at the UK equivalents in the chart above. Because each X covers two W sizes, the UK equivalent is always a range rather than a single number.
How to Measure Yourself for X Sizes
You need a soft tape measure and two minutes. Measure over underwear or a thin layer, keep the tape level and snug but not tight.
- Bust: around the fullest part of your chest, under your arms and across your back.
- Waist: around your natural waist, the narrowest point, usually just above your belly button.
- Hips: around the fullest part of your hips and bottom, feet together.
Then decide which measurement to size by:
- Tops, blouses and dresses with no stretch: size by your bust.
- Trousers, shorts and skirts: size by your hips, then check the waist is elasticated or adjustable.
- Stretchy knits and rib fabrics: you can usually take the smaller size if you are between two.
- Coats and jackets: size up if you plan to layer a jumper underneath.
Why Is My 2X a Different Size in Every Shop?
Three reasons. First, there is no legal standard for clothing sizes in the UK or the US, so every brand writes its own chart. Second, X sizes are often designed for a specific fit (relaxed, oversized, fitted), and an oversized 2X will measure much bigger than a fitted 2X. Third, fabric matters: a 100% polyester woven dress has zero give, while a polyester-elastane rib top stretches a size either way. That is why reading the measurements beats reading the label every time.
Plus-Size Pieces to Try in 1X–4X
All of these are in stock in 1X, 2X, 3X and 4X. Check each product's size chart for that piece's exact measurements.
- Pink Plus Size Leopard Puff Sleeve Mini Dress Women UK – £40.38. 100% polyester, so size by your bust. Puff sleeves give room through the upper arm.
- Green Plus Size Floral Frilled Collar 3/4 Sleeve Dress Women UK – £44.82. A frilled collar and 3/4 sleeves; easy for work or a lunch out.
- Leopard Print Long Sleeve V Neck Tunic Plus Size Cardigan Women UK – £20.06. A longline tunic cardigan for layering over tees and dresses.
- Grey Reversible Double Wear Plus Size Sweatshirt Women UK – £31.09. Reversible, so two looks for one price.
- Stripe Colorblock Collar V Neck Plus Size Long Sleeve Top UK – £34.68. A collared V-neck stripe top that tucks into jeans or wide-leg trousers.
- Plaid Pearl Ruffled Short Sleeve Knit Plus Size Festive T-Shirt UK – £28.56. Red plaid knit with pearl trim, ready for the Christmas season.
Green Plus Size Floral Frilled Collar Dress, 1X–4X.
Browse everything in our Curves & Plus Size collection or go straight to plus-size dresses. For outfit ideas, read our complete UK plus-size style guide.
Frequently Asked Questions
What size is 1X in UK sizes?
1X is roughly a UK 18–20, with a bust of about 109–117cm (43–46in). Some brands cut 1X as a UK 16–18, so check the product chart.
What UK size is 2X?
2X is usually a UK 20–22 (bust about 117–124cm), though some brands label it UK 22–24.
What UK size is 3X?
3X is usually a UK 22–24, with a bust of about 124–132cm (49–52in).
What UK size is 4X?
4X is usually a UK 24–26, with a bust of about 132–140cm (52–55in).
Should I size up or down if I am between X sizes?
Size by the measurement that matters for the garment: bust for tops and dresses, hips for bottoms. In stretchy knits you can usually take the smaller size; in non-stretch fabric or coats, go up.
Is 1X bigger than XL?
Yes. 1X is the first plus size and is cut fuller through the bust, hips and arms than a standard XL.
