Emma Watson wants people to monitor the "carbon impact" of their closets.
The 'Little Women' star has partnered with online thrift store thredUp to promote their Fashion Footprint Calculator, which helps users see for themselves how their fashion habits are impacting the environment.
In an Instagram post, Emma shared: "Our closets impact the planet and climate more than you might realize, which is why I am proud to partner with @thredUP to launch their new Fashion Footprint Calculator (link in bio!) They created an easy to use tool, and I'm so excited to help people discover the carbon impact of their wardrobes, and steps you can take to lighten your fashion footprint. (sic)"
Emma went on to explain how the footprint calculator works, and listed some simple ways people can make changes to the way they shop which can help save the environment.
She added: "They'll tell you what your fashion footprint is equivalent to a number of flights, exactly how many pounds of CO2 it produces and how you fare compared to an average consumer. Small changes, such as thrifting instead of buying new, supporting sustainable brands, and air-drying your clothes, can make a HUGE difference.
"My friends at @goodonyou_app are also included in the directory at the end of the quiz, where you can get more info on the impact of your fashion choices. (sic)"
The 29-year-old actress has become known for her activism, and has helped launch a number of initiatives, including the UN Women campaign 'HeForShe', and a legal advice line for women who are suffering sexual harassment at work, which was set up last summer.
The new advice line is managed by Rosa, which is the UK Fund for Women and Girls, and offers advice provided by Rights of Women, a charity which aims to legally help women dealing with unwanted attention.
In a statement supporting the service, the 'Harry Potter' star said: "It finally feels like people are realising the scale of the problem, and I'm certainly hopeful that with global standards such as the recent International Labour Organisation treaty on harassment at work, we'll start to see a new climate of prevention and accountability on this issue domestically."