Members of the platform have expressed outrage after an update resulted in listings displaying inaccurate size information.
The second-hand shopping app has updated its measurement guidelines for women's and children's garments failing to inform all shoppers about the modification.
Many shoppers and sellers are posting online saying Vinted listings now show a modified sizing category versus the original listing because of the remapping.
Vinted explained the revised method more closely matches similar services.
It has advised users to review their products and adjust the sizing manually if necessary, resulting in member annoyance.
Earlier, the measurements included a single numeric size and a letter, such as S/8 or M/10.
The revised method features an alphabetical indicator and numerical range like S/UK 8-10.
For certain items, the measurements have been reclassified - like an L measurement was formerly size 12 but now shows as UK 16-18.
Frankie Bridger, who creates plus-size fashion videos, stated the update "complicates both purchasing and selling".
"Rarely do manufacturers list XL as sizes 20-22," which is what Vinted now does.
A different member, based in Glasgow, said garments she listed with size 14 tags were appearing on the platform as larger sizing 20-22.
"If anyone [who is] size 20-22 buys them they may become frustrated," she explained.
A different user, based in Derby, said she had been left angered because the modification necessitated personal updates the sizing for "all her products".
"Personally, this is quite irritating, since I have chronic health issues and Vinted sales have been crucial for me since losing part of my income," she explained.
The platform boasts over 100 million members, comprising 18 million UK members.
It has become a favored option to second-hand platforms like eBay and Depop.
This isn't the first time that an unexpected update on the platform has faced criticism: earlier, the service retracted a modification regarding delivery choices following member complaints.