Hollywood star Emma Watson wants people to monitor the "carbon impact" of their closets.

In an Instagram post, Watson wrote: "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."

Watson explained 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, reports femalefirst.co.uk.

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 hige difference.

She concluded: "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."

Watson has gained popularity 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.