The WW2 veteran, 99, originally wanted to raise £1,000 for NHS Charities Together by completing 100 laps of his garden before his 100th birthday on 30 April.
Known to many as Captain Tom, the inspirational pensioner completed his challenge on 16 April just one week after launching the “Captain Tom Moore's 100th Birthday Walk for the NHS” fundraiser on JustGiving.
On Friday evening, Captain Tom’s total hit £20,005,301, after more than 977,000 people worldwide contributed to his fundraising cause.
War hero Tom is continuing to smash his target - and has vowed to keep walking as long as the money keeps coming.
His efforts have captured the hearts and minds of the nation - with over nearly one million people singing a petition calling for the Captain to be given a knighthood by the Queen.
And the Duke and Duchess of Cambridge offered their congratulations to Captain Tom on Friday morning - calling him a “one man fundraising machine”.
Latest coronavirus news, updates and advice
Speaking to BBC Breakfast, Prince William said: “It's incredible. It's amazing. What I love also is that he's a 99-year-old war vet, he's been around a long time, he knows everything and it's wonderful that everyone has been inspired by his story and his determination.
“I think he's a one man fundraising machine and God knows what the final total will be but good on him. I hope he keeps going.”
Captain Tom said of his achievement on BBC Radio 2’s Zoe Ball Breakfast Show: “It really is absolutely enormous isn't it. That sum of money is very difficult to imagine but it's coming in so well.”
His daughter, Hannah Ingram-Moore said: “Tom is clear that as long as people believe that he's worth investing in, he will keep walking because this is for such a phenomenal cause.
“We know that this story will have a life to it, so as long as people are donating we'll keep supporting my father to do it and he will keep walking.”
Good Morning Britain host Piers Morgan contributed £10,000 of his own money to boost the coffers on his JustGiving page, tweeting: "This extraordinary man @captaintommoore has single-handedly galvanised Britain into raising cash for NHS heroes."
As he completed his final lap around his garden, Tom was saluted by four soldiers from Yorkshire Regiment who had travelled to support him.
Upon finishing his 100 laps, he told BBC Breakfast: “I never ever dreamt I would be involved in such an occasion. We're doing so well, and knowing that the reason we started off was for the NHS.
“I think you've all got to remember that we will get through it in the end, it will all be right but it might take time. All the people finding it difficult at the moment, the sun will shine again and the clouds will go away.”
You can donate to the Tom’s Walk for the NHS campaign at JustGiving.com.