Glossary

What is a size guide? E-commerce definition

June 4, 2026

A size guide (size guide, sizing chart) is a resource on an online store that helps the customer choose the right size before purchasing: XS to XXL table, measurements in centimeters, fit (slim, regular), US/UK/EU equivalences, or recommendation according to body shape. Indispensable in fashion, sports, or footwear, it reduces returns, purchase friction, and customer service inquiries related to product variations.

Summary

Size guide definition

Why the size guide is important in e-commerce

Expected content in a size guide

Setting up a size guide on Shopify

Points of vigilance to be aware of

In summary

Associated terms, FAQ, and going further

Size guide definition

The size guide answers the question: which size variant should I order for my body or my usage? It complements photos, description, and the variant selector on the product page.

Common formats are to be read as practical reference points to understand the topic well.

Correspondence table: columns for size (S, M, L) and measurements (chest circumference, hips, sleeve length in cm); Guide by category: "How to choose your size" page for dresses, jeans, shoes; Fit finder / quiz: a few questions (usual size, body shape) followed by a recommendation; Model info: "The model is 1.78 m tall and wears size M" on the product page; Guide by brand: Nike vs Adidas vs house brand, as measurement charts differ.

Useful distinctions are to be read as practical reference points to understand the topic well.

Size guide vs variant selector: the selector allows you to choose S/M/L; the guide explains which choice to make; Size guide vs Product FAQ: the FAQ answers specific, one-off questions; the guide structures the reference measurements; Size guide vs fit (cut): the fit describes the volume (slim, oversized); the guide indicates which size to take for that cut; Global store guide vs product-specific guide: some items have an atypical fit (runs small/large); Static guide (PDF, image) vs dynamic guide (app, Shopify metafields depending on SKU).

Why the size guide is important in e-commerce

Without a clear guide, the customer hesitates, orders two sizes "just in case", or abandons the purchase. In online ready-to-wear, size uncertainty is one of the leading causes of returns and customer service contact.

Reduce returns: fewer size exchanges, lower logistics costs (product return); Increase conversion: confidence to click "Add to cart" (conversion); Limit abandonment: size doubt = pre-purchase friction (cart abandonment); Relieve support: fewer tickets like "what size for 1.70m?" (customer support); Enhance credibility: transparent brand, reviews mentioning "fits well" (customer reviews); Optimize CRO: testing guide placement, wording "slim fit" (CRO); Cross-border: EU/US/UK equivalences prevent errors on international B2C.

A well-designed size guide is a profitable lever: low production cost, direct impact on net margin after returns.

Expected content in a size guide

Elements to include in an effective size guide:

Measurements in cm (and inches if US customer base): chest, waist, hips, inseam; How to measure: "take your chest circumference flat, without pulling tight"; Fit indication: "this model runs small, take one size up"; Visual diagram: silhouette with measurement arrows; Comparison: "if you wear an M at [brand X], take an S here"; Returns / exchanges: policy reminder if the size does not fit.

Use case: a DTC jeans brand displays a "Size Guide" link on each product page that opens a table: size 32 = waist circumference 84 cm, straight fit. The description specifies "fits true to size, refer to the guide". Customer reviews tag "true to size" or "size up +1". After a few months, returns due to "incorrect size" drop significantly and the mobile add-to-cart rate increases. The team updates the product FAQ with two generic questions linking back to the guide.

For shoes or accessories (belts, rings), adapt the units (EU/UK shoe size, circumference in mm).

Setting up a size guide on Shopify

Shopify does not provide a complete native size guide, but offers several approaches (Shopify Help Center):

Dedicated page: Online Store > "Size Guide" pages, linked from the footer menu or product page; Product Metafields: "sizing_chart" field (HTML or image) displayed in the theme via Liquid; Custom theme block: "Size & Fit" accordion under the Add to Cart button; Sizing Apps: Kiwi Sizing, Smart Size Guide, Fit Quiz recommend a size based on measurements; Shopify Variants: "Size" option on each product; the guide documents the measurements → option mapping; Theme 2.0: reusable "Size chart" section assigned by collection (dresses, pants).

Typical merchant workflow:

The process is as follows: Measure production samples (flat measurements); Create a table per collection or per SKU if the fit varies; Publish via page or metafield; link from the product page template; Test on mobile (table readability, horizontal scroll); Update after recurring feedback or change of supplier.

An AI chat like Qstomy can complement the guide by answering "I am 1.65 m, 62 kg, what size?" using the published size chart.

Points of vigilance to be aware of

To ensure this topic remains useful for the store, it must above all be linked to a concrete goal: better informing the customer, making operations more reliable, or improving conversion. Visible without excessive scrolling: "Size Guide" link above or next to the variant selector Mobile-first: responsive tables, not just an unreadable PDF on a smartphone Honesty about the fit: "runs small/large" avoids disappointment and returns Clear units: cm by default in France, cm/inches toggle if needed Photos on model + measurements reinforce the guide Sync with stock: do not recommend an out-of-stock size (stock management)

The main points to watch out for concern data consistency, readability for the buyer, and the team's ability to maintain the system over time. Analyze returns: "too small/large" reasons feed guide updates Generic guide copied from an Asian supplier (inconsistent grids) Guide hidden in footer with no link on the product page Blurry image table or untranslated on multilingual store Forgetting shoes / accessories in a mixed store Never updating after a change in patronage (pattern)

In summary

In summary, size guide = help choosing the right size variant via measurements and correspondences Formats: cm chart, fit, quiz, model info, brand equivalences Challenges: fewer returns, higher conversion, less friction and CS Shopify: page, metafields, theme block, sizing apps Visible placement, mobile, honest fit, continuous updates.

Associated terms, FAQ, and going further

Associated terms

Product variant: size = variant option.
Product FAQ: additional Q&A about size.
Purchase friction: doubt about size = obstacle.
Customer reviews: field feedback on the fit.
Product return: consequence of choosing the wrong size.

FAQ

Is a size guide mandatory in e-commerce?

Not legally mandatory, but highly recommended as soon as you sell sized items (clothing, shoes). Without a guide, returns and abandonment increase.

Where should the guide be placed on the product page?

Ideally near the size selector: text link, ribbon icon, or "Size and fit" accordion. Avoid hiding it only in the footer.

Size guide and Shopify variants: how to link them?

Create the Size option (S, M, L, 38, 40…) on the product. The guide documents which option to choose based on measurements; sizing apps can pre-select the variant.