How to Add a Size Guide to Your BigCommerce Store

Why Your BigCommerce Store Needs a Real Size Guide

If you sell apparel on BigCommerce, the size guide is one of the most consequential elements on your product page — and one of the most neglected. Shoppers can't try anything on, so the size guide is doing the job a fitting room does in a physical store. Done well, it prevents the fit-related returns that make up the bulk of fashion's roughly 25% return rate. Done poorly (or hidden), it quietly sends shoppers to bracket-order or abandon the cart.

This guide covers how to add a size guide to BigCommerce properly, and — just as importantly — when a static guide isn't enough and you should reach for a size recommendation instead.

The Options on BigCommerce

BigCommerce gives you a few ways to add a size guide, depending on how much control you want:

• App from the marketplace. The fastest route — install a size chart app that injects a guide and manages it for you.
• Product description or custom field. You can embed a chart in the description or a custom field, though this is harder to maintain across a large catalog.
• Theme/template edit. For full control, you can add a "Size guide" trigger and modal directly in your Stencil theme template.

For most merchants, an app or a template-level modal is the sweet spot — maintainable and consistent across products.

Step-by-Step: Adding the Guide

1. Choose your method (app or theme edit).
2. Build or import your measurement chart, ideally with both centimeters and inches for international shoppers.
3. Add a clearly labeled "Size guide" trigger next to the size option, not at the bottom of the page.
4. Configure the guide to open in a modal so it doesn't push your product details down.
5. Assign the correct chart per product type or category.
6. Save and preview on both desktop and mobile.

Placement Is Everything

The single biggest factor in whether a size guide reduces returns is where it sits. A guide buried in a footer tab gets ignored; a guide right beside the size selector gets used at the moment of doubt. This is the same principle that governs conversion on the whole page, which we cover in How to Improve Conversion on Fashion Product Pages.

Use Per-Category Charts, Not One Global Chart

A single store-wide chart is rarely right — a dress, a pair of jeans, and a swimsuit need different measurement tables. Assign charts by product type or category so each garment shows relevant guidance. The best size chart apps automate this assignment, which saves enormous manual maintenance as your catalog grows. The criteria for choosing one are in How to Choose the Best Shopify Size Chart App — the same evaluation logic applies on BigCommerce.

Don't Forget Mobile

Most fashion shoppers are on phones, so test your size guide on a small screen. Confirm the modal is readable and scrollable, the trigger doesn't overlap the add-to-cart bar, and the chart's units toggle (if you have one) is easy to tap. A size guide that breaks on mobile costs more conversions than it saves.

The Limit of Any Size Guide

Here's the honest ceiling: a size guide — no matter how clean — only provides information. It shows measurements and leaves the shopper to translate "38-inch chest" into "Medium or Large in this product." That interpretation gap is exactly where bracketing and size-related returns live, as we explain in Size Chart vs Size Recommendation.

So if you've added a polished size guide and returns still haven't moved, the guide isn't failing — you've hit the limit of the chart-only approach.

When to Upgrade to a Recommendation

Move from a static guide to a size *recommendation* when:

• Fit-related returns stay high despite a clear guide.
• Shoppers bracket (order multiple sizes).
• You sell categories where measurements alone don't predict fit — stretch fabrics, structured cuts, footwear.

You can keep the size guide for reference and layer a recommendation on top for the actual decision. For the wider toolkit, see The Best Size Recommendation Tools.

Keep It Consistent Across Your Catalog

A scattered approach — different chart formats, mismatched units, inconsistent placement across products — quietly erodes trust and creates fit confusion. Decide on a single standard early: where the trigger sits, which units show first, how charts are styled, and how they map to categories. Then apply it uniformly across the catalog.

Consistency matters because shoppers learn your store. When the size guide behaves the same way on every product, customers know where to find it and how to read it, and that familiarity itself reduces hesitation. As your catalog grows into hundreds or thousands of SKUs, an app that automates per-category assignment is what keeps this consistency from becoming a manual nightmare. Build the standard once, automate the application, and revisit it each season as your range evolves.

Where YourSizer Fits

A size guide answers "what are the measurements?" YourSizer answers "which size fits me?" — a product-specific recommendation that picks up exactly where a BigCommerce size guide stops. It embeds next to the size selector and uses 3D body modeling to give each shopper a confident size. See it for brands, the shopper experience, or pricing.

Sources

• Shopify State of Commerce research
• Baymard on size guide usability

Frequently Asked Questions

How do I add a size guide to BigCommerce?

You can install a size chart app from the BigCommerce marketplace, embed a chart in a product custom field, or add a "Size guide" trigger and modal directly in your Stencil theme. Place the trigger next to the size option and assign per-category charts for accuracy.

Where should the size guide appear on a BigCommerce product page?

Right next to the size selector, opening in a modal so it doesn't push product details down. Shoppers look for fit help at the moment they choose a size, so a guide hidden in a bottom tab gets ignored and has little effect on returns.

Will a size guide reduce my returns?

A guide helps by making measurements accessible, but it still leaves the size decision to the shopper, so its impact on returns is limited. To meaningfully reduce fit-related returns, pair it with — or upgrade to — a size recommendation that gives a confident, product-specific answer.