John spoke on the Today show Monday as part of a two-part interview, and the wedding announcement will air on Tuesday.
Same-sex marriage was legalized in England and Wales this weekend, and John says the two might marry as early as this May.
"We'll do it very quietly," the singer says of the ceremony. "But we will do it and it will be a joyous occasion."
"I'm very proud of Britain and the laws that we've seen come into existence since we've been together," John continues. "For this legislation to come through is joyous, and we should celebrate it."
"We shouldn't just say, 'Oh, well we have a civil partnership. We're not going to bother to get married,'" the singer says. "We will get married."
John and Furnish have been in a civil partnership since 2005, and have two children together, Zachary and Elijah. The star also spoke on Today about the 40th anniversary of his album, Goodbye Yellow Brick Road, and says he loves music "as much now as I did [then]."