Why Sizing Based on Guesswork Is Holding Back Sustainability in Fashion

I still remember my first design internship like it was yesterday. One day, I asked the Creative Director how they created the brand’s size guide. His answer?
“I just figured it out.”

That moment stuck with me. Because it meant that sizing decisions – something so crucial to the customer experience – were being made based not on real data, but on assumptions about what women’s measurements should be.

And that’s a problem.

When Sizing Is Guesswork, Sustainability Takes a Hit

In the fashion industry, we often talk about sustainability – using eco-friendly fabrics, improving packaging, reducing emissions. But here’s a question that rarely gets asked:

How can we talk about sustainability if our sizing systems are based on guesswork?

Imagine the number of garments produced every year that never get worn simply because they don’t fit. Ill-fitting clothes don’t just disappoint customers – they contribute to waste, returns, and unsold inventory. And the root cause is often flawed sizing charts that don’t reflect real body measurements.

The truth is, many fashion brands lack the tools to determine whether their size charts match their customers’ actual body types. Without that feedback loop, they’re essentially designing in the dark.

Poor Sizing = Poor Outcomes

When brands rely on outdated or assumption-based sizing, here’s what happens:

• High return rates due to poor fit
• Unsold inventory that doesn’t match customer demand
• Frustrated shoppers who stop buying from the brand
• Increased environmental waste from overproduction

It’s a lose-lose situation for both businesses and the planet.

Real Data Is the Future of Sizing

To change this, brands need access to real, accurate sizing data – the kind that shows how their customers’ bodies actually measure, grouped by size range and shape. With this data, brands can:

– Build size charts that reflect their real customers
– Identify measurement gaps not currently being catered to
– Design collections that fit better, reduce returns, and improve customer loyalty

So, where does this sizing data come from?

A smart size recommendation tool – like SizeSense.ai – does more than just suggest a size. It collects real customer measurements (with consent) and turns that information into actionable insights. These insights empower brands to finally close the gap between design intent and real-world fit.

Because here’s the mindset of many online shoppers today:
“I’ll just order multiple sizes and return the ones that don’t fit.“

This bracketing behavior isn’t just a hassle for customers – it’s an expensive, wasteful challenge for brands. But with the right sizing tools, it doesn’t have to be this way.

Sizing should never be a guessing game. It should be driven by real data, customer insight, and a commitment to serving people of all shapes and sizes.

When the right size is available – and it fits – everything changes:

• Customers feel confident
• Brands see fewer returns and higher retention
• Sustainability goals actually become achievable

Sustainability starts at the pattern table. And that starts with getting sizing right.