Photo-Based vs Questionnaire-Based Size Recommendation

Photo-based size recommendation measures the shopper's body from a picture, while questionnaire-based size recommendation estimates their measurements from answers such as height, weight and age. A photo gives the tool direct evidence of body shape; a questionnaire relies on averages, so it works well for typical builds but can miss people whose shape differs from the average for their height and weight.

ZeDaq.ai publishes this blog and offers photo-based sizing. Competitor details come only from each company's own homepage, checked November 2026. For an overview of store tools that use either method, see our ranked list of Shopify try-on apps.

How does questionnaire-based sizing work?

A questionnaire tool asks the shopper a few questions, then predicts their body measurements. It compares those predictions with the product's size chart and returns a size.

Common questions include:

• Height
• Weight
• Age
• Preferred fit, such as tight, regular or loose
• Body shape, often chosen from pictures
• A size the shopper wears in another brand

Sizebay is one example. Its homepage (checked November 2026) says shoppers get a clothing size "with only their height, weight, and age."

The strength of this method is low effort. Most people know their height, and the questions take seconds. The weakness is that the tool never sees the body. Two people with the same height and weight can have very different chest, waist and hip measurements.

How does photo-based sizing work?

A photo tool asks the shopper for one or more pictures, usually with a known reference such as their height. AI estimates body measurements from the outline and proportions in the image, then matches them to a size chart.

The number of photos varies by tool:

• ZeDaq.ai uses one photo plus height in a 30-second body scan. The measurements are matched to your own size chart, with a generic UK, US, EU or AU chart as a fallback.
• 3DLOOK says on its homepage (checked November 2026) that it needs two photos and returns over 80 body measurements, delivered through mobile SDKs and an API.

The strength of this method is direct evidence. The tool reads the shopper's actual shape rather than an average. The weakness is effort and comfort. Some shoppers don't want to share a photo, and a poor photo can lead to a poor reading.

How do the two methods compare?

	Questionnaire-based	Photo-based
What the shopper gives	Answers such as height, weight and age	One or more photos, often plus height
Time for the shopper	Usually seconds	Usually under a minute
Sees the real body	No, it predicts from averages	Yes, it reads proportions from the image
Works without a camera	Yes	No
Common error source	Bodies that differ from the average	Poor lighting, loose clothes, bad pose
Privacy concern for shoppers	Weight can feel personal	A photo can feel personal
Uses your size chart	Depends on the tool	Depends on the tool

The last row matters most. Either method can give poor advice if it matches to a generic chart that doesn't reflect how your brand cuts.

Where does each method go wrong?

Every sizing method has blind spots. Knowing them helps you set up the tool well and write better fit notes.

Where questionnaires struggle

• Athletic builds. Muscle is denser than fat, so weight alone can suggest a larger waist than the shopper has.
• Pear and apple shapes. Hips or waist may be much larger or smaller than average for the shopper's weight.
• Guessed answers. Shoppers may round their weight or not know it.
• Body changes. After pregnancy or weight change, older brand sizes may no longer fit.

Where photos struggle

• Loose or bulky clothing. A thick sweater hides the waist line.
• Poor lighting or busy backgrounds. The outline is harder to read.
• Wrong pose or framing. Cropped feet or a tilted phone affect proportions.
• Shoppers who won't share a photo. They need another route, such as your size chart.

How can you reduce errors with each method?

You can't remove every error, but small changes help a lot.

For questionnaires:

• Ask for a size in a brand shoppers know. It gives the tool a second reference point.
• Offer body-shape pictures. Simple drawings help shoppers describe proportions they can't put into numbers.
• Explain why you ask for weight. A short note builds trust and gets more honest answers.

For photos:

• Show an example photo. One picture of a good pose beats a paragraph of instructions.
• Ask for fitted clothing. Leggings and a T-shirt give a far clearer outline than a coat.
• Let shoppers retake. If a photo is blurry or cropped, prompt for a new one rather than guessing.

Which shoppers prefer each method?

Your shoppers' habits matter as much as the technology. Think about who buys from you.

• Shoppers who know their size in other brands often find questionnaires quick and familiar.
• Shoppers between sizes or with uneven proportions may get more from a photo, because the tool reads each measurement.
• Shoppers buying for an event often care more about fit than speed, so they'll spend a minute on a photo.
• Shoppers on a slow connection may prefer answers to uploading an image.

Privacy also shapes the choice. Some shoppers feel uneasy typing their weight, while others feel uneasy sharing a photo. Tell shoppers plainly what you collect, why you need it and how long it's kept. Put that note next to the tool, not only in your privacy policy, so people see it at the moment they decide.

Some stores offer both. They show a size chart for people who prefer to measure themselves, and a photo scan for people who want a direct answer.

A worked example: a bridal boutique

Bridal is the clearest case for direct measurement. A wedding dress has to fit closely at the bust, waist and hip, and the bride may differ by two sizes across those points.

Say a bride is 5 ft 6 in, with a bust that matches a size 8 and hips that match a size 12 in your chart.

• A questionnaire sees her height and weight and suggests the size most people with those numbers wear, perhaps a 10. That may be tight at the hips.
• A photo scan reads each measurement and, with ZeDaq.ai, sizes up to the largest relevant one: the 12. Your seamstress can then take in the bust, which is easier than letting out the hips.

The same logic applies to other close-fitting items, such as tailored suits and evening gowns. Wherever proportions matter more than overall size, direct measurement tends to help.

Our guide to sizing for bridal boutiques covers alteration allowances and how to write bridal charts.

How do you set up either method well?

The method is only half the job. The chart and the page around it decide whether shoppers trust the result.

1. Use body measurements in your chart. List the chest, waist and hip of the person who fits each size.
2. Split charts by garment type. In ZeDaq.ai you add one chart per type: tops, outerwear, dresses and bottoms.
3. Close gaps between sizes. Make each range meet the next so nobody falls between.
4. Give photo tips. A short line, such as "fitted clothes, full body, plain background," improves photo readings.
5. Write a fit note per product. Tell shoppers if an item runs small or large.
6. Test on real people. Ask five people who know their size in your brand to try the tool.

For a wider comparison of tools that use these methods, see our guide to the leading size recommendation apps.

If you're also weighing a style quiz, read size recommendation vs fit quiz apps.

What does ZeDaq.ai cost?

ZeDaq.ai lists its plans on the pricing page:

Plan	Price	Notes
Free	$0	3 try-ons, 3 measurements and 5 invoices a month
Micro	$14/mo
Starter	$49/mo
Growth	$129/mo
Scale	$299/mo

Every paid plan has a 3-day free trial with no card required. Each size scan uses one measurement from your plan.

FAQs

Is photo sizing more accurate than a questionnaire?

It sees the shopper's real proportions, which helps people whose shape differs from the average. Accuracy still depends on a good photo and an accurate size chart.

What photo works best for a size scan?

A full-length photo in fitted clothes, standing straight against a plain background, gives the clearest outline.

Does ZeDaq.ai ask for the shopper's weight?

No. ZeDaq.ai's scan uses one photo plus height.

What if a shopper won't upload a photo?

Keep your size chart visible on the product page so they can measure themselves. ZeDaq.ai doesn't offer a questionnaire mode.

Can I use both methods on one product page?

Yes. Many stores pair a photo scan with a visible size chart, and some add a questionnaire tool too. Keep each option clearly labeled so shoppers know which one they're using.

Does a photo scan work for children's clothing?

Check with the vendor before you use any scan for children. For kids' ranges, an age-and-height size chart is often the simpler choice for parents.