I’m Nithya Sudhir. I collect words, chase patterns, and write about whatever makes me curious.
Do letters make as much sense as numbers to you when you’re deciding what to buy?
For most people, both are useful shortcuts — while letters group measurements into broad, familiar ranges, numbers divide them into narrower ones.
The difficulty for customers, however, is that brands draw those boundaries differently.
In fact, a study examining 120 brands found considerable variation in what the same size label actually meant. Meanwhile, 91% of US and UK shoppers surveyed by Vogue Business said their size changes between brands.
Yet labels still feel more personal.
Research into vanity sizing found that smaller labels generate more positive self-imagery.
Without a fitting room, shoppers must decode each brand’s private sizing language, making size one of DTC’s most underestimated psychological decisions.
It’s Monday. Let’s get into it.
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The impossible job of a size
Size, if you think about it, is a four-letter word that turns a three-dimensional relationship into a one-dimensional label.
The UK’s national SizeUK survey scanned 11,000 people and extracted 130 measurements from each body.
A product page must translate such a complex relationship with so many variables into one answer: S or M.
Getting it wrong costs money.
In a 2023 Coresight survey of 100 US apparel-industry decision-makers, 53% identified size or fit as the leading reason for online apparel returns.
But before a garment ever reaches someone’s door, its size has already shaped their decision.
How we choose a size online
Did you know that shoppers always arrive with a size in mind. Then they look for reasons to trust it, change it or abandon the purchase altogether.
1. “I’m usually a medium.”
Baymard’s usability research found that familiar labels such as S, M and L provide a starting point for many shoppers.
This is due to anchoring. We normally begin with a reference point and adjust from it.
In this case, that reference point is our remembered size.
SPOKE makes this tangible. Its trouser sizing combines 15 waist options, three builds and 10 leg lengths. Shoppers begin with familiar measurements, then choose a narrower, regular or wider fit through the thigh and seat.
Tip: Pair familiar labels with the brand’s regional equivalents and relevant body measurements. Give shoppers something they recognise, then the information to adjust it.
2. “Wait. Why do I need a large?”
When the chart contradicts that familiar size, product information can feel like a personal judgment.
Vanity sizing found that smaller labels encourage positive self-imagery. Conversely, five studies on larger-than-expected sizes found that larger-than-expected sizes lowered clothing evaluations through their effect on appearance-related self-esteem.
This self-threat helps explain why knowing sizes are inconsistent may not soften the sting.
Tip: Describe the garment first: “This cut is narrow through the hip.” Then recommend a size. Explain the fit without defining the person.
3. “But what would it look like on me?”
Next, shoppers imagine where the waist will sit, whether the fabric will cling and where the hem will finish.
This is mental simulation: mentally rehearsing an experience before having it.
Research spanning 11 studies and 5,950 participants found that showing models in the shopper’s own size helped reduce fit uncertainty and improve purchase decisions.
But variety needs organisation. Five studies found that mixing model sizes could make browsing feel harder; filters and hover features helped.
Tip: Let shoppers choose “View on size S, L or 2XL” and keep that preference while browsing.
4. “And if I’m wrong?”
Even after all that checking, uncertainty can remain.
Clear remedies support perceived-risk reduction. In the model-photography research, highlighting free returns made model-size differences less influential on purchase intentions.
Separately, 82% of consumers in the NRF’s 2025 research considered free returns important when shopping online.
Woodies makes its remedy specific. Its Perfect Fit Guarantee covers sizing adjustments on first orders in each product category. Customers can request alterations or remakes within 60 days of delivery, where shipping charges may apply.
You found the dream shirt. You’re between sizes. What do you usually do?
Sizing in the GLP-1 Era
Today, brands face another question: what if a customer expects their size to change?
In a Circana survey, 80% of GLP-1 users anticipated needing new clothes because of size changes.
The easy conclusion is that customers are getting smaller, so brands should manufacture smaller sizes.
And that’s happening: H&M dropped 3XL and 4XL, Amarra introduced size 000, while Mango cut sizes 16–20 from 6.6% of new dress inventory in spring/summer 2025 to 0.5% in 2026.
But shrinking size ranges don’t mean demand for larger sizes is disappearing.
For instance, ThredUp’s purchase volume for large, XL and plus-size womenswear rose 17.4% in 2026 and Quince more than doubled its plus-size collection, from 21 styles to 50.
While some brands are narrowing their ranges, others see room to offer more.
For DTC brands, the opportunity is to understand what customers need next and that means listening beyond sales.
If you never offer someone’s size, their absence from your sales data cannot tell you whether they wanted to buy.
A good size guide should help people find their place in your range. Your range must give them a place to begin with.
That’s all for today. Let me know how you think about sizing in your replies.
How's the depth of today's edition?
See you next week,
Nithya
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