Build a Size Chart as a Fashion Founder: Where to Start When Every Body Is Different
"Customers keep telling me my medium is a small, and I do not know whose measurements I should be using."
I hear that sentence from fashion founders who graded their first patterns, shipped a collection, and then read a stream of comments about sizing that contradicted each other. If you have ever wondered whether you should have fitted your samples on a different body, you are in very good company, and a published industry standard offers a useful starting point.
Why It Is Hard to Build a Size Chart as a Fashion Founder
Sizing has no single rulebook that every brand follows. Each label develops its own fit based on its fit model, its target customer, and its pattern maker, so a medium at one brand can differ from a medium at another. Shoppers know this, which is why they often read sizing comments before they buy.
For a small label, there are practical limits as well. You may have only one fit model, a small sample budget, and a factory that grades patterns by its own rules. Because mistakes show up as returns and reviews, it is easy to feel that your chart is a verdict on your skill instead of a document you can improve.
What Standards and Surveys Say When You Build a Size Chart as a Fashion Founder
ASTM International publishes ASTM D5585-21, a standard table of body measurements for adult women of the misses figure type, sizes 00 through 20.
The standard says its measurements can serve as a baseline when designing apparel, and that the tables help manufacturers develop patterns and garments consistent with the current characteristics of the population, with the aim of reducing consumer confusion and dissatisfaction related to apparel sizing.
According to the listing, the standard also describes six three-dimensional avatars, created by the company Alvanon, to help visualize posture, shape, and proportions.
Size and fit also matter commercially. A 2023 survey by Coresight Research of 100 decision makers at U.S. apparel brands and retailers with at least $10 million in annual revenue found that respondents named size and fit as the most common reason for online returns, at 53 percent.
A few cautions belong here. The ASTM page I reviewed is the store listing, and the tables themselves are sold separately, so I have not read the measurements, and the page does not say whether brands are expected to follow them. The standard covers one figure type and one size range, which will not describe every customer.
The Coresight survey was small, was sponsored by a company that sells body-measurement technology, covered companies much larger than most founder-led labels, and reports the views of respondents and not counts of actual returns.
Even so, the common thread may be useful: a published baseline exists for one major size range, and fit is the reason fashion companies themselves name most often, so a deliberate approach to sizing is worth the time.
Signs You Need to Build a Size Chart as a Fashion Founder With More Care
These signals come from what I see in coaching, and they are everyday observations rather than a clinical checklist:
Your size chart uses body measurements only. It shows no garment measurements, so customers cannot compare the piece with a favorite item.
Customers contradict each other. One reviewer says the style runs small, and the next says it runs large.
You fit every style on one person. The same fit model approves every garment, and nobody else has tried them.
Your chart has never been revised. The numbers came from the first samples, and sales data has not changed them.
If several of these feel familiar, a small round of testing may reduce both the confusion and the returns.
How to Build a Size Chart as a Fashion Founder in Five Steps
Choose your customer and your starting point. Name your target customer, and consider using a published baseline such as the ASTM tables for your size range, if it fits your market. Treat it as a foundation and not as a rule.
Show garment measurements next to body measurements. List the finished measurements for each size, such as bust, waist, hip, and length, so customers can compare the garment with something they own.
Add a short note on the intended fit, such as relaxed or close to the body.
Test every style on more than one person. Ask several people of different shapes within each size to try the sample, and collect honest comments. Pay attention to patterns and not to a single opinion.
Collect structured feedback after launch. Add a short fit question to your return form and your review requests, such as "ran small," "true to size," or "ran large," and revisit the data each quarter.
Revise your chart and say so. When the data shows a style runs small, update the chart and the product page, and let customers know what changed. These steps are my coaching suggestions, and no study cited here tested them for small labels.
What This Looks Like in Practice
I've coached a founder who ran a small label of structured blazers and told me she dreaded reading reviews because half of them said the shoulders were tight and the other half said they were loose.
She had fitted every sample on one model, a friend who was her best sizing guide. We began by comparing the finished measurements of her blazers with the body measurements on her chart.
She invited five customers of different builds to try the next sample, added the finished garment measurements to every product page, and started asking a one-line fit question on every return and review.
After two seasons, she told me the comments had become more consistent, and she knew which two styles to adjust. The business was the same size, and she read her reviews without clenching her jaw.
In my experience as a life coach, the founders I work with who earn lasting loyalty tend to treat sizing as a conversation with their customers, and they keep refining it as they listen.
Your patterns reflect real care, and a size chart that keeps learning helps more people feel that care each time they wear the garment.
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