The system, developed with digital start-up Metail, and managed by We Are Social, requires either two pictures of the body, plus another of the face, or real measurements and a picture of the face, and the system generates 3D virtual images that look like the user.
F&F fitting will then suggest clothing sizes based on the details. Customers can try clothes on their personalised 3D digital bodies online and even dress in a complete outfit and mix and match skirts, jackets, tops and shoes, just as customers would in a real shop.
Tesco is trialling the service via its clothing Facebook page, and will include 50 items at launch, with another 10 added each week during the trial. Customers can add the clothes they like to their Tesco basket.
Emily Shamma, director of Tesco clothing online, said: "We know the main reason people get nervous about buying clothes online is simply because they cannot try them on first.
"Although there has been talk about 'virtual fitting rooms' before, until now the technology has not been able to combine styling, accurate fit and size based on peoples' specific measurements.
"If our customers tell us they like this, we could see real business benefits, not only with more people opting to shop online for clothing, but also helping to reduce returns, commonly caused by people ordering the wrong size."
For added fun, users can modify hairstyles on their virtual selves.
Tom Adeyoola, CEO and founder of Metail, the digital agency behind the virtual fitting room technology, said: "The inspiration behind this technology is about solving one of the biggest problems with online shopping – clothing shape and fit.