How to Find Your Perfect size at And/Or

BRAND SIZING GUIDE · LINGERIE & UNDERWEAR

And/Or runs true to standard UK sizing — but lingerie sizing is its own world, and getting it right makes an enormous difference to how everything you wear on top of it looks and feels.

By Ella Blake  |  Tellar Fashion Hub

And/Or — the ASOS in-house lingerie brand — sizes consistently in standard UK sizing and is genuinely one of the most reliable options at the accessible end of the market. That is the good news. The less straightforward news is that buying lingerie online always comes with its own set of sizing landmines, and And/Or is no exception. I have had a few underwear ordering disasters in my time (a bralette that could have doubled as a hammock springs to mind), so let me save you the bother and walk you through how to get it right first time.

How And/Or Sizing Actually Works

And/Or uses standard UK sizing across its range, which means their knickers, bodysuits, and non-wired pieces follow the familiar 6–18 UK scale. For bras, they use conventional UK bra sizing — so band size in inches combined with a cup letter. Crucially, the two sides of the range are sized independently from each other, which matters more than you might think.

In general terms, And/Or is designed with an inclusive fit philosophy — the brand caters from a size 6 up to a size 26 in some styles, and their extended sizing is one of the things that sets them apart from a lot of competitors at this price point. The sizing itself is consistent and accurate, which makes ordering online far less of a gamble than with some lingerie brands.

A rough guide to their knicker and non-wired sizing:

UK SizeBust (cm)Waist (cm)Hips (cm)UK 679–8161–6386–88UK 882–8564–6789–92UK 1086–8968–7193–96UK 1290–9472–7697–101UK 1495–9977–81102–106UK 16100–10582–87107–112

Always measure yourself rather than going by the size you wear in your regular clothes — lingerie sizing and ready-to-wear sizing are not the same conversation, even when the numbers look identical.

The Bra Sizing Bit (The Bit Everyone Gets Wrong)

Getting your bra size right at And/Or — or anywhere, frankly — starts with two measurements: your band size and your cup size. The band is measured around your ribcage, directly under your bust, and should be snug but not tight. The cup is the difference between that measurement and the fullest part of your bust.

Here is where most women go wrong: they are wearing a band that is too big and a cup that is too small. It is one of the most common lingerie mistakes there is, and it affects everything — your posture, your silhouette under clothes, and your comfort by 3pm. If the band is riding up at the back, it is too big. If the underwire is sitting on breast tissue rather than flat against your ribcage, you need to go up a cup size.

And/Or’s wired styles tend to be true to standard UK bra sizing. Their bralettes and non-wired options have a little more flex and you may find you can size down one if you are between sizes and prefer a snugger fit.

STYLIST’S TIP

If you are new to being properly fitted,M&Soffers free in-store bra fittings and the staff are genuinely excellent. Go once, get your correct measurements, and then apply those numbers confidently when shopping And/Or online. It is one of the most useful things you can do for your wardrobe.

Bralettes vs. Underwired: Does the Sizing Change?

Short answer: yes, a little. And/Or does a strong line in bralettes, which have become one of the most-worn items in the range — they are comfortable, they look brilliant under wide-neck tops and slip dresses, and they are genuinely flattering across a range of cup sizes. For bralettes, And/Or recommends sizing by your UK dress size rather than your bra size, as the construction is more forgiving. If you are in between, go up rather than down — a bralette that is too small will create unflattering lines under clothing and will be deeply uncomfortable by lunchtime.

For their more structured underwired styles, stick to your correct bra size. And/Or’s fuller-bust styles in particular are designed with a deeper cup and a wider underwire, and they work best when worn in the right size rather than approximated.

Bodysuits: The One Where Sizing Gets Complicated

Bodysuits from And/Or are sized to UK dress sizing, but you need to think about both your torso length and your bust when making a choice. If you are long-waisted and fuller on top, you may find a bodysuit pulls uncomfortably at the crotch snap. And/Or’s sizing notes on each bodysuit style are worth reading carefully — they often include fit notes specific to that garment. When in doubt, size up: a slightly roomier bodysuit is wearable, a too-small one is not.

Brilliant Alternatives Across Every Budget

And/Or sits comfortably in the accessible mid-market, but if you want to explore similar or better quality options at different price points, here is where I would send you:

• M&S — Still the gold standard for everyday bras at the high street level. Their Total Support range in particular is exceptional for fuller busts, and their sizing is meticulous. Free fittings in store make them a genuinely brilliant resource.

• Next — Consistently underrated for lingerie. Their multi-pack knickers are excellent quality for the price, and their bra sizing is reliable and well-reviewed. Good range of sizes including extended sizing.

• New Look — A solid choice for on-trend lingerie sets at a very accessible price point. Sizing runs true to UK standard, though their bralettes can come up slightly small — size up if you are between sizes.

• H&M — Their lingerie is better than it often gets credit for. The Comfort line in particular is worth knowing about — soft, well-cut basics that wash well and hold their shape. True to UK sizing.

• Calvin Klein — For the premium everyday underwear drawer, Calvin Klein is the brand most women eventually migrate to. Their sizing is consistent (they use US sizing, so size up one from your UK size), and the quality-to-longevity ratio is excellent.

• Tommy Hilfiger — Similar territory to Calvin Klein — classic, well-made everyday underwear with a sporty edge. US sizing applies, so again, size up one from your UK size.

• The White Company — For soft, considered lingerie in beautiful fabrics — lots of modal and silk blends — The White Company delivers a premium feel without the designer price tag. Sizing is true to UK standard and their customer reviews are consistently helpful on fit.

For something a little more interesting, I am obsessed with Dora Larsen right now — a London-based lingerie brand that does the most beautiful, editorial-feeling sets in unexpected colourways and lace combinations. Their sizing is UK-standard and runs true; their pieces feel genuinely special. Also worth knowing about: Stripe & Stare, a British brand built entirely around the idea of underwear that is actually comfortable. Their knickers in particular have developed something of a cult following, and the fit really does live up to the hype. Both are independent, both are brilliant.

The Bottom Line on And/Or Fit

And/Or is a genuinely reliable, well-sized brand that punches above its weight at the accessible end of the lingerie market. Their inclusive sizing, consistent quality, and good range of styles make them a go-to — but like all lingerie shopping, you will get the best results if you come armed with your actual measurements rather than a guessed size. Measure your band, measure your bust, check your hips for knicker sizing, and resist the temptation to order the size you think you are. Order the size you actually are. Your comfort and your silhouette will both thank you for it.

Get Your Exact And/Or Size with Tellar

Lingerie sizing is one of the areas where getting it right really matters — and it is also one of the areas where most of us have been quietly wearing the wrong size for years. Tellar.co.uk is the UK’s leading free sizing tool, and it exists to take the guesswork out of exactly this kind of shopping moment.

Here is how Tellar works:

• Measure once — bust, waist, and hips (or enter a brand size you already know fits you well)

• Use the Store Size Lookup tool to get your precise recommended size across 1,500+ brands instantly — no more size guide confusion

• Works in your browser, no download required, completely free — every time

Tellar matches your body measurements to each individual brand’s unique sizing rather than applying a generic conversion — so you get an accurate result, not an approximation.

More from the Tellar Fashion Hub — honest, unbiased, always free:

• The Ultimate Clothing Sizing Guide — why brands size so differently, and how to navigate it

• Jean Trends 2026 — the cuts and washes that are worth investing in right now

• Ultimate Guide to Dresses & Best Buys — every style, every body shape, every budget

• Ultimate Guide to Jackets & Best Buys — find the fit that actually works for your frame

The Tellar Fashion Hub is written by real stylists with no brand sponsorship, no paid placements, and no agenda beyond helping you dress brilliantly. Every post is independent. Every recommendation is genuine.

👉 Visit Tellar.co.uk — the UK’s leading free sizing tool

This post was written independently by the Tellar editorial team. No brands featured in this article have paid for inclusion or sponsored this content. All views are our own.