How to Segment Shopify Customers by Size

To segment Shopify customers by size, decide where the size data comes from, label each customer with it (usually a tag), and build a customer segment that uses that label. You can then send restock alerts and new-arrival emails only to people who can wear the item.

This guide covers the data sources, a simple tagging method and how to use the groups. If you also offer virtual try-on on Shopify, the same thinking applies to the size information shoppers give you.

What is a customer segment in Shopify?

According to the Shopify Help Center, segments are dynamic, rule-based customer lists. You build each one by combining filter names, operators and values into a query in ShopifyQL.

Customers are added or removed automatically as they meet or stop meeting the criteria. Shopify suggests using Shopify Messaging to send marketing messages to the segments you create.

Check the filter reference in Shopify's help pages to see which filters your store can use. The ones available can change, so confirm them before you plan a campaign.

Where does size data come from?

You have three realistic sources. Each has a trade-off.

Source	Strength	Weakness
Past orders	Already in your store	Shows what was bought, not always what fit
Customer-provided size	Direct and current	Needs a form or a prompt
Measurements	Most precise	Needs consent and a way to collect them

Start with past orders, because the data exists today. Add the others when you have a way to collect them.

How do you label customers by size?

A tag is the simplest label. It is searchable, easy to read and works with most email and segment tools.

1. Pick a naming pattern. For example, size-top-M and size-bottom-32. Keep it the same for every customer.
2. Separate garment types. A customer can be a medium in tops and a different size in trousers. Use one tag per type.
3. Tag from orders. Find customers who bought a given size and kept it, and add the tag. Skip orders that were returned for fit.
4. Update when it changes. If a customer returns a size and reorders another, replace the tag.

Start with your best sellers. Tagging the whole customer list at once is a lot of work for little extra value.

How do you build the segment?

Open the customer segments area in your Shopify admin and create a new segment. Use the filter that matches your tag, then save it with a clear name such as "Tops size M".

Keep the number of segments small at first. One segment per size and garment type is enough. If you sell many sizes, group them by range, for example small sizes and large sizes, instead of making a segment for every size.

Test with a small email to your own address before you send to a large group.

How can you use the segments?

Send restock alerts to the right people

When a size returns to stock, tell only the customers who wear it. Back-in-stock apps handle individual requests, as compared in the guide to back-in-stock apps for size restocks. Segments cover people who bought before, even if they never signed up for an alert.

Announce new arrivals in their size

Mention the size in the email only if you know it is in stock. A message that says "back in your size" is far more useful than one that says "new arrivals".

Show relevant sizing help

Customers who often return items for fit can get a short sizing guide. Customers who buy plus sizes can get news about that range. The guide to selling plus-size clothing on Shopify covers range-building in more detail.

Support made-to-measure customers

If you sell custom sizes, customers' measurements are the best data you have. See selling custom-size clothing on Shopify for how to collect and store them.

What should you keep in mind about privacy?

Size is personal. Only collect what you need, tell customers why, and follow the rules for email consent where you sell.

Don't put a customer's size in a subject line or any text another person could see. Tell customers how to update or remove their size information.

How do try-on and size tools fit in?

A try-on or size tool helps shoppers choose a size at the moment of purchase. A segment helps you speak to them afterward.

With ZeDaq.ai, a shopper's 30-second body scan produces a recommended size from your own chart. Whether you copy a size into a tag is your decision and your process. If you compare tools before choosing, the roundup of AI virtual try-on apps for Shopify is a place to start.

FAQs

Do I need an app to segment customers by size?

Not always. Shopify's built-in segments work with the data in your store, and tags can be added by hand. An app helps when you have a lot of customers to label.

Should I use tags or metafields?

Tags are easier to start with. Use metafields if you need structured data, such as several measurements per customer.

How often should I update the segments?

Segments update automatically as customers meet the criteria. The tags behind them need updating when sizes change, so review them after each season.

Can I segment by a size customers never told me?

You can only use data you have. Past purchases give you a guess, so label it as one and let customers correct it.