A Size guide is measurement guidance to help your customers select the best-fitting size.
On the Product page, you have the option to have a link to a size guide which will open up as a modal on the product page.
This size guide link can also be a great option to display other information about the product, such as returns instructions, color references, terms and conditions, or materials within the product.
You will first need to add a new page to create your size guide.
Within your Shopify admin, go to Online store > Pages.
Select Add page.
Once you have your size guide page, you must link it to the product page.
Within your theme editor, go to paste your link into the box called Size guide page (this will create a link on your product page).
Change the title of this link by typing your words of choice under Size guide message.
This link then appears on your product page underneath your variants.
When this link is clicked, a page will open to display the size guide.
You also have the option to tag your size guide onto a specific variant - this way, the size guide would only appear on products with that variant.
You can do this by typing the name of the variant into Show on a selected variant; for example, typing in 'Size' would link your size guide onto your size variants.
Leaving this field blank will result in your size guide link appearing on every product page.