A Fendi Baguette handbag from The RealReal.

Buying previously owned jeans instead of new ones saves the planet 279 liters of water and 11 driving miles; a cotton dress, 218 liters of water and 9 miles; a wool sweater, 101 liters and 18 miles, and a viscose top, 20 liters and 6 miles.

Those are tallies made by a sustainability calculator being introduced by The RealReal, allowing its consignors and buyers to understand the extent to which their activities on the e-commerce resale site are softening luxury’s blows to the environment.

The calculator uses proprietary methodology to calculate the amounts of greenhouse gases, energy and water used in the apparel manufacturing process that are saved when products are consigned instead of newly produced.

“If something has a high production impact, that’s even more reason to ensure it has as long a life as possible,” explained Allison Sommer, director of strategic initiatives at The RealReal. “It’s better to buy something used that greatly impacts the planet than to have a new one produced.”

The RealReal also chose Earth Day today to announce that it’s the first resale site to join the Fashion Industry Charter for Climate Action, alongside brands such as Kering and Levi’s, and partners such as Stella McCartney.

“We’re a member of the Ellen MacArthur Foundation’s CE100 USA,” said Julie Wainwright, The RealReal’s chief executive officer. “Joining the charter is a natural next step for us to be an agent for change on a global level. We want to help create solutions that will dramatically reduce fashion’s role in global warming.”

The RealReal has set a goal of reducing its carbon emissions by 30 percent by 2030.

Sommer, who joined one of the charter’s working groups, spearheaded the creation of the calculator. “This is our first and biggest effort to translate what the circular economy means in a tangible way to consignors,” she said. “We understand at a conceptual level that extending the life of something already produced [is beneficial to the planet]. Our goal was to quantify how environmentally friendly an apparel item can be.”

The RealReal, since its founding in 2011, has saved 88 million driving miles and 327 million liters of water or the equivalent of 1.4 billion glasses of water, through the consignment of women’s apparel, according to the company.

Consignors can view sustainability metrics on their My Sale Page, which tracks sales activity and commissions. Metrics will automatically populate for any eligible items or measurable items under My Environmental Settings. The number will grow as a consignor sells more products.

“We don’t own the supply chain of any items we sell, which make this a challenging project,” said Sommer. “Also, the items we sell are extremely diverse. We needed to come up with a structure to create averages for different types of fabric.”

With the help of experts from the Ellen MacArthur Foundation, Shift Advantage, which provides sustainability and corporate responsibility services, and the World Resources Institute, The RealReal was able to calculate percentages for the amount of water and energy used by fabric type.

The RealReal uses the industry-accepted displacement rate of one-third, meaning that for every garment that’s consigned, about one-third of the resources needed to make the same new item are saved.

“A lot of consumer-facing businesses are approaching sustainability from different angles. It’s all positive because it’s raising awareness and getting people thinking about the fact that products aren’t made in a vacuum,” Sommer said. “We’re now having a conversation beyond the fiscal benefits [commissions] and we’re discussing the environmental benefits. We’re making people aware that consigning is a desirable alternative to buying fast fashion.”

With research on the most common types of women clothing now done, The RealReal plans to extend the calculator to other textile items. “We want as much visibility as possible. We know from consignor surveys that sustainability is one of the leading reasons people choose to consign with us. We’re speaking to a value that’s already top of mind,” Sommer said. “The ability to see your personal impact is quite motivating.”