How to Add a Size Chart to Shopify Without a Paid App

A size chart looks like the simplest feature on a product page – a table, some numbers, done. It is also one of the most commonly outsourced to a paid app, often for a feature a well-built theme can already do natively. Here is what a size chart actually needs to do, why so many themes leave it out anyway, and how to check whether yours already has it before you install anything.

What a size chart actually needs to do

A size chart has three jobs, and most implementations only manage one of them. First, it needs to show the right table for the right product – a fitted shirt and an oversized hoodie do not share one chart, and neither do two different footwear brands with different lasts. Second, it needs to be reachable from the product page in one tap, not buried three clicks into a help centre article a shopper has to go looking for. Third, it needs to let a shopper compare their own measurements against the table without doing the arithmetic themselves – a toggle between centimetres and inches, or a highlighted row for “you are probably a size M,” does real work that a static image never can.

Most size-chart apps get the first job right and stop there – one table, uploaded once, linked from a small text link near the variant picker. That covers a single-product store. It falls apart the moment a catalogue has more than one fit, because the app was never built to serve a different table per product without manual re-uploading for each one.

Metafields are the native mechanism

Shopify's own answer to this is a product metafield – a structured field you define once, then fill in per product, that a theme can render consistently wherever it belongs. A size chart stored as a simple table in a metafield, rather than as a single flat image glued to the whole store, means every product carries its own correct chart, and updating one product's sizing never risks breaking another's layout. We cover the mechanics of setting metafields up in a separate guide; the size chart is one of the more common uses for exactly this pattern.

Done this way, a chart is data rather than a picture. That distinction matters more than it sounds: a picture cannot highlight a row based on a shopper's answer to “what's your usual size,” and it cannot be reused across a collection of otherwise-different products that happen to share one sizing standard. A table stored as structured data can do both.

The pattern itself is simple. Store the table as a short multi-line text field – first line the column headers, one line per size after that – and let the theme's template turn it into an HTML table wherever a size chart belongs. Every product gets a correct, current chart, filling in the field takes less time than uploading and cropping an image, and nothing about updating one product's numbers can accidentally break the layout on another.

Why so many themes fake it with one static image

Building a per-product, structured size chart is more development work than dropping a single popup image into a theme, so a lot of themes simply do not bother. The result looks fine on a demo with one product line, and then breaks down quietly the moment a real catalogue mixes fitted and relaxed cuts, or footwear sized in UK, US and EU standards on the same store. The shopper does not see a missing feature; they see a chart that is wrong for the item in front of them, which is worse than no chart at all, because it actively misleads rather than simply staying silent.

This is the same trade covered elsewhere on this journal for wishlists and quick view: a genuinely useful version of a small feature is real development work, and plenty of themes leave the harder version out, which is exactly the gap most paid size-chart apps exist to fill.

Fit varies more than a single chart admits

Even within one brand, cut varies by style – a boxy silhouette and a slim one rarely share a chart honestly, even if the label size is the same M or L on both. Publishing one generic size guide across an entire catalogue papers over that difference and pushes the confusion onto returns instead of the product page, which is the more expensive place for it to surface. If two styles fit differently, say so, and give each its own chart or its own fit note rather than a single table doing double duty.

The same honesty applies to model measurements. A line noting the model's height and the size they are wearing in the photos costs one sentence and answers the single most common pre-purchase question – “will this look on me the way it looks in the photo” – better than the size chart alone ever will. This is also where a returns policy earns its keep as marketing rather than small print: a shopper who is unsure between two sizes is far more likely to buy both and return one when the return process is stated plainly next to the chart, rather than left for them to hunt down separately.

Where this matters beyond clothing

Apparel is the obvious case, but it is not the only one. Footwear needs the same table treated across three regional sizing standards rather than one. Fine jewellery needs a ring-size chart with a simple way to measure at home, ideally paired with a size selector that reads as a set of size chips rather than a dropdown of unfamiliar numbers – a pattern we use across our jewellery editions. A multi-brand catalogue selling several suppliers' products under one roof needs a chart per brand, not one chart quietly applied to all of them, since brands frequently disagree on what a “medium” actually measures.

Checking whether your theme already has it

Before installing an app, check three things directly on a real product page. First, is there a visible size-guide link or icon next to the variant picker, not hidden in a footer menu. Second, does opening it show a table specific to that product, rather than one generic image reused everywhere – try it on two different product types and see whether the chart actually changes. Third, does it work on a phone without needing to pinch and zoom to read the numbers, since most Shopify traffic arrives on mobile and a chart that only works on a wide desktop screen is solving the smaller half of the problem.

A theme that passes all three has already replaced the feature most size-chart apps are sold to provide.

Where LUMIERE fits

Our free LUMIERE theme renders size and fit information from product metafields directly on the product page – no app, no separate popup to maintain, just a definition you fill in once per product. It costs nothing to try against your own catalogue before deciding anything. See the setup in the documentation, or browse the rest of the range, including the ring-size chips used on our jewellery editions, at Kiosk.