Next week will see him set out every day for a different 26.2-mile route, with one seeing him run 187 laps of the track at his old primary school.
The 19-year-old found he had a talent for running when he took part in a fun run in 2014 and then started to do the Shrewsbury park run.
Jack started to run competitively and joined Wolverhampton and Bilston AC.
Last year he won the Wolverhampton Half Marathon and also completed the Copenhagen Marathon in a time of two hours and 50 minutes.
During the spring lockdown Jack found himself running up to 90 miles a week and came up with the idea of a week of back-to-back marathons to raise funds for charity.
"I chose Cancer Research UK because my Grandad has been poorly with cancer and also the charity that my mum, Dawn, works for, the Omega charity in Shrewsbury," he said.
Anyone who wants to support Jack can do so at crowdfunding/jack-pickett-7in7
He will begin his marathons attempt on November 9 running 13 miles along the canal from Tesco in Ellesmere and back.
Other routes include one around the lanes around Cockshutt, another taking in 16 laps of Colemere and around based around Ellesmere. His plan to run the Shrewsbury Park Run eight times had to be shelved because of the new lockdown restrictions.
He said: "I hope to start each day at 9am and if people see me on route I would be really grateful for words of encouragement."
Jack has been training for his week of marathons and says the weekend runs, at Colemere on the Saturday and on Sunday five kilometre laps from Tesco, along Elson Road, Cae Goody Lane and Grange Road, are going to be the toughest.