Setting Up Your Size Chart for Accurate Size Recommendations

To set up your size chart for accurate size recommendations, enter body measurements (not garment measurements) as a minimum and maximum for each size, with one chart per garment type. Then close any gaps between sizes and test the chart on real people before you go live.

A size recommendation tool is only as good as the chart behind it. If the chart is vague or patchy, the suggestion will be too. This guide covers the format, the data checks and a worked example. For how the scan itself works, see the overview of AI size recommendation.

What format should your size chart be in?

ZeDaq.ai reads your chart as ranges of body measurements. Each size has a lowest and highest value for the measurements that matter for that garment.

Keep these rules in mind:

• Body, not garment. Record the chest of the person who fits a medium, not the flat width of the shirt.
• One unit. Choose centimeters or inches for each chart and stick to it.
• One chart per garment type. Tops, outerwear, dresses and bottoms each get their own chart.
• Your own labels. Use the size names shoppers see on your site, such as "S", "UK 10" or "Size 2".

Which measurements does each garment type need?

Only enter what decides the fit. Extra columns add work without making the suggestion better.

Garment type	Key measurements
Tops	Chest
Outerwear	Chest, with room for layers
Dresses	Chest, waist and hips
Bottoms	Waist and hips

If you have more than one fit within a type, such as slim and relaxed shirts, the ranges should reflect the fit you sell. A relaxed fit allows a wider body range per size.

How do you upload or enter your size chart?

1. Open the chart editor. In the Shopify app, open Your size chart. On other platforms, go to Dashboard → Size charts.
2. Pick a garment type. Start with your best-selling category.
3. Choose your unit. Centimeters or inches.
4. Enter each size. Add the minimum and maximum for each key measurement.
5. Test a shopper. Type a set of measurements and check the size it suggests.
6. Save, then repeat for the next garment type.

Any garment type you leave empty uses a generic UK, US, EU or AU chart. The article on what happens without a size chart explains that fallback.

How do you check your size chart data quality?

Bad data is the most common reason a recommendation feels wrong. Run this checklist before you save:

• Ranges meet. If medium ends at 96 and large starts at 98, a shopper at 97 falls in a gap. Make the edges touch.
• No overlaps. One body measurement should point to one size, not two.
• Sizes grow steadily. A jump that is much bigger than the others is often a typing error.
• Units match. A chart that mixes inches and centimeters gives strange results.
• Labels match the product page. The recommended label must be one the shopper can pick.

When a shopper is between sizes, ZeDaq.ai sizes up to the roomier one. Clean ranges keep that rule working as you'd expect.

Worked example: a dress chart

Here is an example chart in centimeters. It is for illustration only, so check your brand's own chart before using any numbers.

Size	Chest (cm)	Waist (cm)	Hips (cm)
S	82–88	64–70	88–94
M	88–94	70–76	94–100
L	94–100	76–82	100–106

A shopper measured at chest 90, waist 69 and hips 99 sits in M for chest and hips, and S for waist. The tool sizes up to the largest relevant measurement, so it suggests M. That is the size that won't feel tight across the hips.

What about made-to-measure or custom sizing?

If you cut each piece to the client, a fixed chart may not fit how you work. You may still want standard sizes for ready-to-wear lines. The guide to sizing for made-to-measure brands covers how to mix the two.

A clean chart also helps with the wider problem of exchanges and returns. The guide to where fit-related returns come from looks at the other causes worth fixing.

How much does it cost to test your chart?

The Free plan includes 3 measurements a month, enough to test a chart on your own team. Paid plans start with Micro at $14 a month, and every paid plan has a 3-day free trial with no card required.

FAQs

Can I paste in my existing size guide?

You enter it as ranges per size in the chart editor. If your guide lists single values, turn each into a range that meets the next size.

Should I use garment or body measurements?

Use body measurements. The scan measures the shopper's body, so the chart must describe bodies too.

How many charts do I need?

One per garment type you sell, up to four: tops, outerwear, dresses and bottoms.

What if my fit changes between collections?

Update the ranges for that garment type when the cut changes. Then test a few known shoppers again.