Online Clothes Sizing Guide: Measure, Compare, Buy

The most reliable online clothes sizing guide is a habit, not a chart: take a handful of body measurements once, compare them with the garment measurements and fabric details on each product page, and choose your size from those numbers rather than from the letter on the label. Do that consistently and most of the guesswork disappears. The rest of this guide lays out the full process, from measuring yourself to deciding what to do when a garment arrives and does not quite work.

It is the hub for our buying-online articles. Where a step deserves its own guide you will find a link, and once you know what you need, you can browse the ADDMPS shop with a list of numbers in hand rather than hope.

Why sizing online is harder than in a shop

In a store you touch the fabric, see the fit and can try three sizes in ten minutes. Online, three things work against you. First, a letter or number size is a brand’s own label, not a standard: a medium from one brand can equal a small from another. Second, product photos show one model in one size, often clipped or pinned at the back. Third, fabric behaviour is hard to judge on a screen. A structured wool jacket and a stretch jersey dress both say “size 8”, but they will tolerate very different amounts of error. The solution is to replace impressions with numbers and to read the fabric before the photograph.

Step 1: Take your measurements once, and write them down

Use a soft tape measure and measure over thin clothing or bare skin, standing relaxed and breathing normally. Keep the tape level and snug but not pinching.

• Bust or chest: around the fullest part, under the arms, across the shoulder blades.
• Natural waist: the narrowest point of the torso, roughly above the belly button. Bend sideways to find the crease.
• Hips: around the fullest part of the seat, usually about 7 to 9 inches below the waist.
• Shoulder width: from the edge of one shoulder bone to the other, across the back.
• Sleeve length: from the shoulder point to the wrist bone with your arm slightly bent.
• Inseam: from the crotch seam to the ankle bone, best measured on a pair of trousers that already fit.
• Neck (for shirts): around the base of the neck where a collar sits, with one finger of room.

We break down each measurement with common mistakes in our guide to reading clothing size charts. Store the numbers in your phone and re-check twice a year, because bodies and habits change.

Step 2: Measure a garment you already love

This step is the single most useful thing you can do. Lay your best-fitting jacket, shirt, trousers or dress flat, and measure it across the chest, waist, shoulders, length and sleeve. Compare those numbers directly with the garment measurements on a product page. A garment measured this way beats any chart, because it accounts for how much ease you like: the extra room between your body and the fabric. If a retailer lists garment measurements, choose by the ones that match your reference garment. If it lists only body measurements, allow for ease yourself: roughly 3 to 4 inches around the chest for a slim, fitted jacket and 4 to 6 inches for a classic tailored one, both layered over a shirt, less for a stretch knit, more for a relaxed cut.

Step 3: Read the product page like a technician

Fabric composition and stretch

A small share of elastane, often 2 to 5 percent, gives comfort and forgiveness, while 100 percent cotton, linen or wool will not stretch much. If you are between sizes, lean smaller in stretch fabrics and larger in rigid ones. Our explainer on reading fabric labels shows what the percentages mean. Always check the product page for the fabric composition, since one style can vary from another.

Cut, model information and length

Note whether the item is described as slim, regular, relaxed or oversized, and what size and height the model wears if given. Compare the model’s height to yours to judge length: a hem at the model’s knee will land lower on someone shorter. Where the page lists back length or inseam, use it.

Lining, structure and details

Lined and structured items, such as blazers, have less give. Details such as shoulder pads, high waistbands and fixed cuffs change the way a garment fits, and the fewer adjustable points, the more careful you must be about size.

Keep a personal fit log

A note on your phone pays off quickly. For each brand you buy from, record the size you took, how it fitted (shoulders snug, waist generous, sleeves long) and whether you kept it. After three or four purchases you will see patterns, such as one label running narrow in the shoulder or another running long in the leg, and you can adjust your choice before ordering instead of after. Add a line for anything you altered and what it cost, because that tells you whether buying a size up and tailoring is worth it for that kind of garment.

Ease: how much room should a garment have?

Ease is the difference between your body measurement and the garment measurement, and it is the reason two people with the same chest size can want different sizes. A close-fitting knit or stretch top might have almost no ease, a shirt usually has 3 to 4 inches around the chest, a tailored jacket about 4 to 6 to allow for a shirt underneath, and an oversized cut can have far more. Decide what look you want before you compare numbers. If you want an oversized coat, buy your normal size and check the drop of the shoulder; if you want a sharp blazer, prioritise shoulder width and chest, and check whether the waist is fitted.

Step 4: Decide between sizes with a simple rule

When your measurements fall between two sizes, use these rules of thumb:

• For anything with a shoulder, like a jacket or shirt, choose the size that fits your shoulders and alter the rest.
• For trousers and skirts, choose the size that fits your largest measurement, usually the hips or seat, and have the waist taken in.
• For dresses, size to the bust or hip, whichever is larger, and use a wrap or waist tie if available.
• For knitwear and stretch pieces, take the smaller size if you prefer a close fit and the larger if you prefer a relaxed one.
• For shirts with a collar, size to the neck first, then check the body length and sleeve.

Tailors can shorten, take in and hem cheaply but can rarely let out much or move shoulders. That asymmetry means it is usually smarter to size up and alter than to size down and hope. See which suit alterations are worth paying for for the fixes that are cost-effective.

Step 5: Buy with the return window in mind

Every online purchase carries a small chance of a miss, and a sensible plan reduces the cost of one. At ADDMPS, eligible unworn items with tags can be returned within 30 days of delivery, and delivery and return details are on the shipping and returns page. Read them before you order, not after. To make the window work for you, try garments on the day they arrive, in the shoes and underwear you intend to wear, and decide within a few days. Our article on return policies and fit tips before you buy has a full checklist for keeping returns rare.

How to run a proper try-on at home

1. Prepare. Wear the shoes, underwear and shirt you would normally pair with the item. Try on in good light in front of a full-length mirror.
2. Check the basics. Shoulders, chest or bust, waist and length. Sit, squat, raise your arms and walk.
3. Take photos. A photo from the back and side shows problems the mirror hides.
4. Style it. Try it with two actual outfits from your wardrobe, not a hypothetical one.
5. Decide. Keep it, tailor it or send it back. If it needs more than one significant alteration, the size is probably wrong.

Keep the tags and packaging until you have decided, since eligible items must be unworn with tags to qualify for return.

What to do when the size is right but the length is not

Length is the most common fit complaint online and the most fixable. Trouser and skirt hems, sleeve ends on jackets and shirts, and the hem of a dress can all be shortened cheaply by most tailors, while lengthening depends on how much fabric was left inside the hem. If you are tall, check for a stated inseam or back length before ordering and look for hems with spare fabric. If you are petite, price in a hem alteration before you decide on a purchase, and remember that high-waisted, cropped and wide-leg items may need a tailor for the proportions to work.

Sizing by category: quick rules

• Blazers and jackets: shoulders decide everything. Check shoulder width, sleeve length and chest ease. The blazer fit guide explains how to check each one.
• Shirts and blouses: neck or chest, then sleeve and body length. If the shirt is worn tucked in, allow for more length. Cuff and collar details are in our article on dress shirt collar and cuff fit.
• Trousers and jeans: waist, rise, thigh and inseam matter together. A garment with an inch of stretch behaves differently from rigid denim.
• Dresses: bust, waist and hip, plus length. Zipper position and lining affect how easy it is to get in and out of.
• Knitwear: width at the chest and sleeve length, with attention to whether the fibre will relax over wear.
• Watches: the measurements are wrist circumference, case diameter and lug-to-lug length. Our watch size and wrist measurement guide is the reference.
• Swimwear and undergarments: stretch and support vary between brands, so use the brand’s own chart carefully and check hygiene and return conditions before trying items on.

Common online sizing mistakes

These are the errors that cause most disappointing parcels.

• Trusting the letter size instead of the numbers.
• Comparing yourself to the model without checking the model’s height and size.
• Ignoring stretch: a rigid twill and a jersey knit are not the same size even at the same label.
• Ordering several sizes of everything, which increases returns and slows decisions. Order a second size only when you truly sit between two.
• Waiting until the last days of the return window to try things on.
• Forgetting that international labels differ, as discussed in the size chart guide.

FAQ: Buying clothes online

How do I know which size to order if I am between two?

Decide by the garment. For structured pieces and anything with shoulders, take the size that fits your shoulders and get the rest altered. For trousers, size to your hips. For stretch fabrics, take the smaller size for a fitted look.

Do I need to measure myself every time I shop?

No. Measure once, save the numbers, and update them if your body changes. Then compare them with each product page. Measuring a well-fitting garment you own is a shortcut that works across brands.

Is it better to buy a smaller or larger size online?

Larger is usually safer if you have access to a tailor, because clothes are easier to take in than let out. If you prefer not to alter, follow the garment measurements and choose the size that gives the ease you like.

What should I do if something arrives and does not fit?

Check whether it could be fixed by a hem, sleeve or waist adjustment. If it cannot, return it promptly while it is still unworn with tags, using the return details you checked before ordering.

Once you have your numbers, shop women’s wear or men’s wear at ADDMPS and compare each piece with your own reference garment before ordering.

Edited by the ADDMPS Style Team.