Mia Simpson is eight years old, goes to St Patrick's School in Lithgow and on Saturday will be cutting off 38 centimetres of her beloved hair.

Mia has been growing her hair for quite some time and has decided to chop a fair chunk of it off all in the name of helping others.

Mia wanted to fundraise in memory of family friend Briony Sheather who lost her battle with cancer in July this year, so she set up a McGrath Foundation page where people could donate.

Mia initially set a modest fundraising goal of $250, but in the first day she had already raised more than $1000 and it continues to climb. As of December 3 she has raised $4313.

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Mia said she was excited for people to see her new hair cut and wasn't nervous.

"I hope my hair helps someone that has cancer have a nice wig and I hope the money raised helps the nurses that looked after Briony," she said.

Mia's proud mother, Jenna Simpson said Mia told her she wanted to do something after she saw what Briony went through.

"She's only eight years old and she's seen Briony go through her battle and cut off her hair, and so Mia wanted to help people that are going through the same battles," she said.

"We thought, well, this could be a good way to support the McGrath Foundation. They gave so much support to Briony and her family so we wanted to try and give back to them.

Mia's lopped locks will be sent to Sustainable Salons and used to make wigs for people who have lost their hair to radiation treatment.

Sustainable Salons Managing Director and Co-Founder Paul Frasca said she was moved by Mia's generosity.

"The significance of what Mia did here is incredible - not only did she raise vital funds for the McGrath Foundation, but her hair is so crucial in making sure that there's enough supply to make the wigs needed," she said.

"When Sustainable Salons first approached the ponytail donation process more than five years ago, there was not even half the amount of hair needed coming through to the correct channels. Now to date we have collected 90,000+ ponytails thanks to the generosity of Mia and many other ponytail donors."

Mia's hair will be cut by her Aunty, Missy Peters who cut Briony's hair when she started treatment as well.

"All of her teachers have been very supportive of her and her friends are excited to see her new haircut. So their excitement I think is spurring her along as well," Jenna said.