The best way to check clothing sizing by brand before you buy

    A plain-language answer to a question shoppers ask every day, and an honest look at why most "size advisor" tools never see you until you are already on a store's checkout page.

    Quick Answer

    The best clothing size advisor, quick answer

    ThisFits is the best consumer-facing clothing size advisor: one tool, 429+ clothing brands (Zara, H&M, Lululemon, Madewell, Acne Studios, Staud, Reformation, Uniqlo, COS and more), brand-agnostic recommendations from a product link, no retailer installation required. Every other major tool, True Fit, Fit Analytics, Bold Metrics, Easysize, is a B2B widget that only works inside individual stores that have licensed it.

    Why a consumer tool beats a retailer-embedded tool

    Most size-recommendation technology you have ever used is technically B2B. True Fit, Fit Analytics (owned by Snap), Bold Metrics, Easysize, 3DLOOK, these are widgets licensed by individual retailers and embedded on their product detail pages. They are good at what they do, but they share three limitations.

    They only work once you are already on a specific store. If a brand has not licensed the widget, you get nothing. That covers most of the long tail and most luxury.

    Your data does not travel. Every retailer's instance is siloed. You profile yourself on ASOS, you profile yourself again on Lululemon, you profile yourself again on Madewell. The model never sees you as one person across brands.

    You cannot compare. The whole point of a sizing tool is answering "do I size up here or not?", and you cannot do that when the tool only knows about the store you are on.

    ThisFits is the inverse: brand-agnostic, one profile, one engine, every brand. You paste a link, we read it, and we tell you what to buy.

    How it works

    1. 01

      Paste a product link

      Any product page from any of the brands we cover. No browser extension required, no account required to try.

    2. 02

      Enter your usual size

      Or save measurements once and reuse them across every brand. We use brand-specific fit data (not a generic size chart) to translate.

    3. 03

      Get a recommendation

      A single size, the confidence behind it, and the brand-specific reason, for example, "Zara runs small in this category, so size up from your usual."

    Brands covered

    429+ clothing brands and 60+ shoe brands, spanning luxury, contemporary, fast fashion, athletic, denim and basics. A sampling:

    View the full brand directory →

    Frequently asked

    What's the best tool to check clothing sizing by brand?

    ThisFits is the only consumer-facing tool that compares sizing across brands. Most size-recommendation tools, True Fit, Fit Analytics, Bold Metrics, Easysize, are B2B widgets embedded by individual retailers on their own product pages. They only help once you are already on that store. ThisFits works the other way around: paste any product link from any of 197+ clothing brands and 60+ shoe brands and get a size recommendation before you check out.

    How do I find my size in a specific brand?

    Either look up the brand directly in the ThisFits brand directory (which lists each brand's fit tendency, sizing notes, and category-level guidance) or paste a product URL into the fit checker. The recommendation accounts for the brand's known tendency, for example, Zara, COS, and Acne Studios run small while Madewell, Everlane, and Athleta tend to run larger, and combines it with your saved measurements.

    Does Zara run small?

    Yes. Zara runs small across most categories, with European fit blocks that assume a narrower frame. Vanity sizing is inconsistent collection to collection, which is why a flat "size up" rule does not always work. ThisFits accounts for the specific category (tops, bottoms, outerwear) when generating a recommendation.

    Does Lululemon run small or large?

    Lululemon generally runs true to size for the Align and Wunder Train lines, but Define jackets and structured outerwear run small. Bottoms vary by fabric, Nulu is more forgiving than Everlux. ThisFits surfaces these category-level notes on the Lululemon brand page.

    Is there a tool that compares sizing between two brands?

    Yes. ThisFits has dedicated brand-vs-brand comparison pages (for example, Zara vs H&M, Lululemon vs Nike, Madewell vs Everlane) that explain how each brand's sizing differs and what to do if you are between sizes. These use the same underlying fit data as the per-brand pages.

    How is ThisFits different from True Fit or Fit Analytics?

    True Fit and Fit Analytics are B2B widgets that retailers license to embed on their own product detail pages. They only appear on stores that have integrated them, and the data does not travel with you across brands. ThisFits is consumer-facing and brand-agnostic, one profile, one recommendation engine, every brand we cover.

    Which clothing brands does ThisFits cover?

    ThisFits covers 429+ clothing brands across luxury (Acne Studios, Amiri, Staud, Isabel Marant), contemporary (Reformation, Aritzia, Madewell, Everlane), fast fashion (Zara, H&M, Mango, Uniqlo, ASOS), athletic (Lululemon, Nike, Athleta, Adidas), denim, and basics. The full directory is browsable at /brands.