"I really hate running," said Freddie, eight, who is a pupil at Malmesbury Primary C of E. "My granny has a really hard job, so I wanted to do something hard to help.
"I enjoyed it and I think it kept me fit - but I really don't like running!"
So, with the help of his mum, Laura, he decided to try to raise £50 by running a mile a day.
"He finished his challenge to run a mile each day for seven days running," she said.
"He took a different route around Malmesbury each time but managed to complete the mile each time. I was recording the distance on my FitBit.
"His Nanny Linda works as an intensive care nurse at Baslidon Hospital in Essex. She was so emotional when she heard Freddie had done this and raised all this money, she burst into tears. He said he wanted to do something to make her smile."
His other grandmother, Nana Sharon Hamilton said she could not be prouder of her grandson.
"We watched videos of him doing his run," she said. "And he clearly finds it hard, but he just kept going. This is the hardest thing he could have done."
Freddie's original target of £50 was busted quickly as friends and family got behind the cheery eight-year-old - who is nine next week. One of his Nana's friends offered to make masks for just £2 if the donation went to Freddie's cause.
"The local pub - The Somerford Arms - gave him a cake to say well done," said Sharon. "And we also entered him and his efforts into a competition with Wentworth Puzzles about people doing good things. He didn't win - but they sent him a puzzle anyway to say they were so impressed with what he had done."