A size guide can exist on a product page and still fail its job. A shopper selecting “M” needs to know whether the guide describes the garment or their body, which units it uses, and where to measure. If the information is hidden behind a generic footer link or a small icon, its presence in the site map means little at the point of choice.
The fix begins with the product, not the template. Sizes may differ across suppliers, cuts, and categories. A universal chart copied from another product can be worse than no chart if it looks authoritative while giving the wrong measurements.
Check the decision sequence
Open a best-selling item on a phone and attempt to choose a size without prior knowledge of the brand. Notice where your eye moves: product photo, size selector, guide, reviews, add-to-cart. Can you open the guide without losing the chosen color? Does the guide identify the item or cut? If you measure in inches but the chart lists centimeters, is the conversion obvious? Is the table readable without sideways zoom?
Next compare the numbers against the actual supplier specification. For each SKU, record whether the displayed measurements are body or garment measurements, the measurement method, and tolerances if supplied. Do not infer fit from nominal labels alone. If product photos include a model size, include the relevant model measurements only when accurate and permissioned.
Rewrite the guide as an action
Put a “Size guide” control beside the size options. Start with a one-line instruction such as “Measure around the fullest part of your chest; compare your body measurement to the chart.” Name the units in the column headers. If a product has a nonstandard fit, explain it in ordinary language tied to measurements, not vague claims such as “true to size.” State where the shopper can ask for help before ordering.
Do not load every product with an enormous generic chart. A separate guide may suit a category with many measurements; a small table may suit a single product. What matters is whether the shopper can find the right answer at the decision point.
Run a task test and check the order record
Ask someone unfamiliar with the store to choose a size from their own measurements. Watch without coaching. Could they find the guide, identify the correct row, and return to the same variant? Then check whether the selected size appears correctly in the cart and confirmation email. This last step is a commerce test; better copy does not repair a wrong variant mapping.
ARCHV can review the product-page content and mobile presentation as a scoped project. Theme behavior, variant mapping, supplier data, returns analysis, and app changes require separate commerce discovery. Request a website estimate with an affected product URL, the supplier chart, and examples of buyer questions.
Evidence and further reading: A Shopify merchant discussion about size-guide use illustrates the owner problem; W3C guidance on labels and instructions supports clear control wording. The forum thread does not measure how widespread the problem is.