How to Shop Online When You're Between Sizes

Being between sizes is not a niche predicament. Size charts jump in fixed increments (typically two inches or more between a medium and a large) while actual bodies land anywhere along that range. If your bust matches one column and your waist matches the next, the chart has no answer for you, and the "when in doubt, size up" folk wisdom fails as often as it helps. The good news: there is a repeatable method for choosing well, and it doesn't require luck. It requires knowing what to look at and in what order.

Step one: find the garment measurements, not the size chart

Most shoppers don't realize that a typical size chart describes a body, not a piece of clothing. It says, in effect, "we designed the medium for someone with a 38-inch chest." What it doesn't say is how much room the designer added on top of that: the ease. A boxy overshirt might carry six inches of ease; a fitted knit might carry none, or even negative ease that relies on stretch.

Garment measurements (sometimes labeled "product measurements" or tucked behind a "measurements" tab) describe the item itself, laid flat. When a retailer publishes them, they beat the size chart every time. Compare the garment's actual chest width against a shirt you own and love, and you've replaced guessing with arithmetic. Retailers vary in how much they disclose: Uniqlo is unusually good about publishing flat garment specs (we break them down in our Uniqlo size chart and fit guide), while many fast-fashion sites offer only a generic body chart. When measurements are missing, treat the listing as higher-risk and lean harder on the other signals below.

Step two: read the fabric before you pick a number

Fiber content is a fit signal hiding in plain sight. A garment with 2% or more elastane (also listed as spandex or Lycra) will forgive a borderline size call; 100% cotton with a rigid weave will not. Knits stretch by construction even without elastane: a jersey tee has give that a woven poplin shirt never will. So the same between-sizes body can safely take the smaller size in a stretch knit and should usually take the larger size in a rigid woven.

Denim deserves its own paragraph, because it moves after purchase. Rigid, 100% cotton jeans typically relax up to an inch in the waist with wear, which argues for buying them snug. Heavily stretched denim, on the other hand, tends to bag out at the knees and seat over a day of wear, so a between-sizes shopper is usually better off going down. Cut matters too: a 501 and a slim taper resolve the same waist number very differently, which is why we map each fit block in our Levi's size chart and fit guide.

Step three: let the silhouette break the tie

Once you know the fabric, the garment's intended shape tells you which direction to round. A few rules of thumb that hold across most brands:

• Structured and tailored pieces: size up. Blazers, button-front shirts, and rigid trousers have hard limits: a button placket that gapes or a shoulder seam that pinches can't be styled away. Extra room, by contrast, can often be tailored or belted.
• Oversized-by-design pieces: size down, or stay true. If the model photos show a deliberately slouchy fit, the volume is already built in. Sizing up on top of intentional oversize usually reads as wearing someone else's clothes.
• Compression and activewear: stay true or size down. Performance fabrics are engineered with negative ease; sized up, leggings sag and waistbands fold. Brands like Lululemon cut with this assumption baked in (see our Lululemon size chart and fit guide for how their numeric sizes translate).
• Dresses and jumpsuits: fit the largest measurement, alter the rest. One-piece garments have to clear every part of you at once. Choose for the bust or hip (whichever maps to the bigger size) because a waist can be taken in far more easily than a bodice can be let out.
• Layering pieces: think about what goes underneath. A coat that fits perfectly over a t-shirt in July may not close over a sweater in January.

Step four: practice return-policy hygiene

When the signals still don't settle it, ordering two sizes is a legitimate strategy, but only if you do it deliberately. Before checkout, confirm three things: the return window (and whether it starts at order date or delivery date), whether returns are free or fee-based, and whether the item is final sale (clearance, intimates, and heavily discounted items often are). Keep tags attached and packaging intact until you've made a decision, try things on within a day or two of arrival rather than letting the bag sit, and put the return deadline in your calendar the day the order ships. A between-sizes gamble is only low-stakes when the exit door is actually open.

One caution: don't make double-ordering your default for every purchase. It ties up money, creates deadline pressure, and a meaningful share of returned clothing is never resold. Reserve it for genuinely ambiguous calls: rigid fabrics, unfamiliar brands, no published garment measurements.

Step five: keep a personal measurements note

The single highest-leverage habit is also the least glamorous: measure yourself once, properly, and keep the numbers where you shop (a phone note works fine). Record chest or bust, natural waist, hip, inseam, and shoulder width, plus the flat measurements of one or two garments that fit you perfectly. Our step-by-step measuring guide walks through how to take each one accurately with an ordinary tape measure.

Then annotate as you go. Every time an order arrives, add one line: "Brand X medium tee — slightly snug in shoulders" or "Brand Y 32-waist — runs a full size big." Within a few months you'll have something no size chart can offer: a record of how sizes behave on your body, brand by brand. Sister brands often share fit blocks, so a note about one can inform another; Gap and Old Navy are a classic example, which our Gap and Old Navy fit guide covers in detail.

The between-sizes mindset

Falling between sizes feels like a personal inconvenience, but it's really just where the industry's rounding error becomes visible. Sizes are coarse buckets; you are a set of precise measurements. Shop from the measurements (the garment's and your own) and the buckets stop mattering. The shoppers who return the least aren't the ones with "standard" bodies. They're the ones who stopped trusting the letter on the label and started trusting the tape.