Importance of Size Charts: Why Proper Sizing Matters in Garment Industry

Pick up two t-shirts labelled “Medium” from two different Indian brands, and there’s a good chance they won’t fit the same way. One might sit snug, the other loose. This isn’t a manufacturing mistake. It’s the result of size charts that are built differently, or in many cases, borrowed from other countries’ body data altogether. For anyone learning pattern making, understanding why size charts matter isn’t just an academic exercise. It shapes how garments are cut, how retailers plan inventory, and how comfortable your customer feels the moment they try something on.

Reaching the maximum number of customers 🔗

A size chart is essentially a translation of population data into garment measurements. Instead of guessing at proportions, manufacturers use anthropometric surveys, which record real body measurements across large groups of people, to figure out which sizes will fit the highest number of people with the fewest number of size categories. This is why size charts exist in the first place: they let one grading system serve an entire market instead of every garment being made-to-measure.

India offers a clear example of why this matters. For decades, the domestic apparel industry has largely worked with size charts adapted from US and UK standards, even though Indian body proportions differ from Western populations in meaningful ways. To fix this, the Ministry of Textiles sanctioned INDIAsize, a national sizing survey conducted by the National Institute of Fashion Technology, to build a size chart based on actual measurements of the Indian population rather than borrowed assumptions. The project eventually scanned over 26,000 people across multiple regions of the country and produced a set of size charts specific to Indian body types, something the industry had never had access to before.

This kind of population-based approach lets a manufacturer plan a production run knowing, in advance, roughly what percentage of buyers fall into each size band. That’s a far more reliable starting point than designing around a single fit model or copying a chart used elsewhere.

Helping retailers stock the right size range 🔗

Once a manufacturer has a dependable size chart, retailers benefit just as much. Buying teams use size charts, along with historical sell-through data, to decide the size ratio for each style: how many smalls, mediums, and larges to order for a particular store or region. A store in one city might sell more of certain sizes than a store elsewhere, and a good size chart gives retailers a consistent baseline to adjust from, rather than starting from scratch every season.

Reducing overstocking and understocking 🔗

Without accurate size data, retailers either overbuy sizes that don’t sell, tying up capital in unsold stock, or underbuy popular sizes and lose sales to customers who simply can’t find their fit. Both scenarios hurt margins. A dependable size chart, backed by real body-measurement data, gives buyers confidence that their size curve actually reflects demand rather than habit or guesswork.

Better fit, fewer alterations for the customer 🔗

For the customer, the payoff of a good size chart is simple: clothes that fit properly straight off the rack. That reduces the need for tailoring alterations and builds trust in a brand’s sizing consistency across different styles and collections.

The stakes here are larger than they might seem, especially in online retail. Poor fit is consistently cited as the biggest driver of apparel returns, and industry research places size and fit issues among the leading causes of high return rates in fashion e-commerce. In the Indian context specifically, researchers studying the case for a national sizing survey noted that garment returns linked to poor fit have been estimated at 30 to 40 percent, a figure that climbs as online apparel shopping grows. Much of this stems from brands using size charts built on instinct and experience rather than verified measurement data.

When a size chart is accurate, a customer buying a Medium from one collection can reasonably expect a similar fit from another collection by the same brand. That predictability is what turns a one-time buyer into a repeat customer.

The economic impact of size charts on production costs 🔗

Size charts also play a direct role in cost planning, and this is where manufacturers have to make trade-offs. Every additional size added to a style means an extra cutting marker, more fabric consumption calculations, more stock keeping units to manage, and more inventory sitting in a warehouse. Offering too many sizes drives up production and holding costs. Offering too few sizes cuts costs but leaves a chunk of the target market with no well-fitting option.

Finding the right size curve 🔗

This is why grading, the process of scaling a base pattern up or down across a size range, depends so heavily on a well-researched size chart. A manufacturer needs to know not just what sizes exist, but roughly what proportion of the target population falls into each one. That data determines the size curve, or how many units of each size to produce relative to demand. Get this wrong, and a business either overproduces sizes nobody buys or runs out of the sizes everybody wants. Get it right, and the size chart becomes a tool for balancing customer coverage against manufacturing efficiency.

Standardisation and quality control 🔗

Beyond fit and cost, size charts function as a technical reference point. They keep garments consistent across different production batches, different factories, and sometimes different countries manufacturing for the same brand. A size chart tells every production line, in exact centimetres or inches, what a size 38 chest or a size M waist should measure, which is what allows quality checks to be objective rather than a matter of individual judgement.

Internationally, standards bodies have tried to formalise this. The ISO 8559 series, for instance, sets out how size designation and body dimensions should be defined and communicated, so that manufacturers, brands, and retailers can communicate size information consistently and reduce fit-related returns. Even so, no single global sizing system has ever been adopted universally. Attempts at an international standard go back to 1969, when a technical committee was formed under the International Organization for Standardization to explore a common sizing system, involving more than 30 participating countries. The effort concluded that a single international system wasn’t practical, mainly because body proportions vary too much from one population to another.

Why India needed its own standard 🔗

That conclusion is exactly why country-specific size charts matter. A size chart built on American or European body data will always be an approximation when applied to Indian consumers, because the underlying proportions it was designed around are different. The INDIAsize project’s charts, developed after years of measurement and analysis, resulted in 27 body-size charts covering different height groups and body shapes, giving Indian brands a genuinely local reference for the first time. As more manufacturers and retailers adopt standards like this, sizing across the industry should become more predictable, reducing the confusion customers currently face when labels like Small, Medium, and Large mean different things from one brand to the next.

For students of pattern making, this is the practical takeaway: a size chart isn’t just a table of numbers to plug into a grading rule. It’s the outcome of research into who a garment is actually being made for, and it shapes decisions all the way from the cutting table to the retail shelf.

What do you think? If Indian brands widely adopt a shared, population-based size chart like INDIAsize, do you think it would meaningfully reduce the confusion shoppers currently face between brands? And as a pattern maker, how would working with a research-backed size chart change the way you’d approach grading a new style?

References

1. https://www.business-standard.com/india-news/one-parameter-less-confusion-india-moves-towards-standard-clothing-sizes-126073000775_1.html
2. https://www.pib.gov.in/newsite/PrintRelease.aspx?relid=176888&reg=48&lang=2
3. https://nift.ac.in/indiasize/
4. https://www.jetir.org/papers/JETIR2303088.pdf
5. https://www.researchgate.net/publication/364718041_INDIAsize_-_Planning_and_Execution_of_National_Sizing_Survey_of_India
6. https://standards.iteh.ai/articles/blog/clothing/clothing-standards-quality-fit-innovation
7. https://www.sciencedirect.com/topics/engineering/sizing-system