We used Fibr to analyse the fabric composition of 17,365 products across six major fashion retailers. The goal: find out which brands actually use natural fibres and which ones are quietly dressing you in plastic.
No opinions. No brand partnerships. Just fabric data.
The Overall Numbers
More than a third of all products across these brands contain polyester. Some brands are far worse than others.
Rankings: Average Natural Fibre Percentage
Each product’s fabric label was parsed to calculate its natural fibre percentage. These are the averages by retailer.
* Aritzia (81 products) and ASOS (34 products) have small sample sizes. Their rankings should be interpreted with caution.
What the Data Shows
Bershka is the surprise leader among large-sample retailers. With 9,339 products analysed, it averaged 62.7% natural fibres — ahead of its Inditex sibling Zara (60.6%) and competitor Mango (59.3%). That’s not a huge gap, but it’s consistent across a massive product catalogue.
Reformation’s positioning doesn’t match the data. Despite marketing itself as the sustainable choice, Reformation averaged 57.0% natural fibres — lower than Bershka, Zara, and Mango. It does excel in one area (more on that below), but its average composition tells a different story than its branding.
ASOS is overwhelmingly synthetic. Even with a small sample (34 products), the pattern is stark: only 41.9% natural fibres on average and 55.9% of products being polyester-heavy.
Products That Are 100% Natural Fibre
Average percentages can mask the distribution. A more revealing question: what share of each retailer’s products are made entirely from natural fibres?
| # | Retailer | % Products 100% Natural | Sample Size |
|---|---|---|---|
| 1 | Aritzia * | 67.9% | 81 |
| 2 | Reformation | 52.9% | 399 |
| 3 | Bershka | 45.7% | 9,339 |
| 4 | Zara | 43.4% | 5,226 |
| 5 | Mango | 40.0% | 2,246 |
| 6 | ASOS * | 26.5% | 34 |
This is where Reformation redeems itself. Over half its products (52.9%) are 100% natural fibre — a higher rate than any large-sample fast fashion brand. When Reformation goes natural, it goes all the way. But when it doesn’t, the synthetics drag its average down.
The Polyester Problem
How many products at each retailer are polyester-heavy — meaning 50% or more of the garment is polyester?
More than one in four Zara products is majority polyester. At ASOS, it’s more than half. Meanwhile, Reformation keeps polyester-heavy products to just 5.3% of its catalogue, and Aritzia (small sample) had none.
Key Takeaways
- No retailer is “all natural.” Even the best performers have significant synthetic content in their catalogues.
- Marketing doesn’t match reality. Reformation, despite its sustainability branding, has a lower average natural fibre percentage than Bershka, Zara, and Mango.
- You can’t judge by brand alone. Every retailer sells a mix of natural and synthetic products. The only way to know what you’re getting is to check each product’s composition individually.
Methodology
This analysis is based on 17,365 products scraped from six online fashion retailers in 2026. For each product, Fibr parsed the fabric composition from the product page and calculated the percentage of natural fibres (cotton, linen, wool, silk, cashmere, hemp, and other plant or animal fibres) versus synthetic fibres (polyester, nylon, acrylic, elastane, and other petroleum-derived materials).
Sample sizes vary significantly by retailer: Bershka (9,339), Zara (5,226), Mango (2,246), Reformation (399), Aritzia (81), and ASOS (34). Results for Aritzia and ASOS should be treated as indicative rather than conclusive due to their small sample sizes. Products with missing or unparseable fabric data were excluded from the analysis.
The “polyester-heavy” threshold was set at ≥50% polyester by weight in the garment’s stated composition. “100% natural” means the garment’s composition lists only natural fibres with no synthetic content.