Free Size Charts for Your Online Store

Fit is the single biggest reason clothing comes back. Put a working size calculator on your product pages with one line of HTML. No signup, no monthly app fee, and nothing your customers type is ever collected.

Why this is worth ten minutes

You already know the number that hurts: somewhere around a quarter of online apparel orders come back, and fit is the reason customers give more than any other. One 2025 consumer survey found 61 percent of shoppers had returned clothing simply because it did not fit (figures collected in Shopify's guide to sizing charts). Sizing is also the reason people give for choosing a physical store over your website: in a shop they can try it on, and on your product page they are guessing.

A static size chart image helps. An interactive calculator helps more, because it does the conversion arithmetic your customer would otherwise get wrong. It also answers the question they actually have. That question is "what size am I in your sizes," not "what does 40 mean."

How it works

Every calculator on Sizeaholic can be embedded on your store, free, on any plan, on any platform that lets you paste HTML. The embed runs the same code as the page on our site: same formulas, same cited sources, same measuring guidance. When we improve a calculator, your embed updates automatically. There is nothing to install and nothing to maintain.

<iframe id="sizeaholic-shoe-size-converter" src="https://sizeaholic.com/embed/shoe-size-converter/" style="width:100%;max-width:520px;height:900px;border:1px solid #e3e8f0;border-radius:12px;" title="Shoe Size Converter" loading="lazy"></iframe>
<p style="font-size:13px;">Calculator powered by <a href="https://sizeaholic.com/shoe-size-converter/">Shoe Size Converter</a> on Sizeaholic</p>
<script>window.addEventListener("message",function(e){if(e.origin!=="https://sizeaholic.com"||!e.data||e.data.sizeaholic!=="height")return;var f=document.getElementById("sizeaholic-shoe-size-converter");if(f&&e.source===f.contentWindow)f.style.height=e.data.value+"px";});</script>

Copy code

Swap shoe-size-converter for whichever calculator fits the product. The full list of slugs is on our embedding page, and every calculator page has a </> Add to your website button that hands you that calculator's finished snippet.

Which calculator for which store

Adding it to your platform

Shopify

Go to Online Store, then Themes, then Customize. Open the product template, add a block or section of type Custom Liquid where you want the chart to appear, and paste the snippet in. Save, and it shows on every product using that template. If you would rather have it on one page only, create a page and paste the snippet using the </> HTML view in the rich text editor.

WooCommerce

Edit the product, and in the description add a Custom HTML block with the snippet. For every product at once, add it to a shared block or your product template in the site editor.

Anything else

Squarespace (Code block), Wix (Embed HTML), BigCommerce, Magento, WordPress, or plain HTML: paste the snippet anywhere page HTML is accepted. The iframe is self-contained.

You do not need to tune the height. The last line of the snippet is a small listener: the calculator tells the iframe how tall it needs to be and the frame resizes itself, including the moment a shopper gets their size and the result makes it taller. The 900 pixels in the snippet is just the starting value.

If your theme strips script tags, paste the rest anyway. The frame keeps 900 pixels and scrolls internally, exactly as it did before, so you lose the automatic fit and nothing else.

What these calculators do, and what they do not

Worth being straight with you, because it decides where they help. Our calculators convert between sizing systems and turn body measurements into standard sizes. They do not know your patterns. If your jeans run a half size small, no general calculator can know that, and any tool that claims otherwise is guessing with confidence.

So the honest way to use these is as the first half of a pair. The embed handles the part that is genuinely universal: what a US 9 is in EU sizes, how to measure a neck, how a knuckle measurement becomes a glove size. You supply the part only you know, which is how your specific garments run. A line of your own next to the embed, something like "our slim fit runs one size small, consider sizing up," is worth more than any app, and the two together answer the customer's real question.

That distinction has a name in the trade: our tools give body measurements, and what your customer ultimately needs is how those relate to your garment measurements. Providing both is what the best size guides do. We wrote the whole thing up for shoppers at body vs garment measurements, including an ease calculator, so publishing your flat measurements costs you a table and answers most of the fit questions your inbox currently absorbs.

Privacy, and why your legal page stays short

The calculators run entirely in the visitor's browser. Measurements are never transmitted, never stored, and never reach us or you. There is no account, no database, no tracking pixel inside the calculator, and nothing to disclose in a cookie banner on the calculator's behalf. For stores selling to the EU or UK, that is one less data processor to document. Our privacy policy spells it out, and the page around the embed remains governed by your own policy.

The license, in plain words

Embedding is free for any store, commercial or not, with no traffic limit and no revenue share. Keep the attribution link under the calculator, use the snippet as provided, and do not present the calculator as your own work. The full wording is in our Terms of Use. That is the entire deal, and there is no upsell behind it.

Need one we have not built?

If you sell something whose sizing deserves an honest calculator and we do not have it yet, tell us. Several of our tools exist because somebody asked. We build them, you embed them, and they stay free.

Frequently asked questions

Last updated 31 July 2026