"Rio is out of reach. I'll be 27 then and swimming, especially for distance swimmers, is a young person's game," Adlington, who finished third behind 15-year-old American Katie Ledecky in the 800 metres freestyle at the London Games, told the Mail on Sunday.
"If I was a sprinter I'd go to Rio. But I don't have an ounce of sprinting in me, and that's why my Olympics are over," added the golden girl of British swimming.
Adlington, who holds the world record in the 800 freestyle, is Britain's most successful Olympic swimmer and before her no British woman had won swimming medals in successive Games.
Having ruled out another Olympics, she has not yet decided whether she will compete at next year's world championships in Barcelona or the Commonwealth Games in Glasgow in 2014.
"Swimming is still in my heart but, physically, I'm ready to finish completely," she said. "If I were to race in Glasgow - and that's an if - then it would be in the 200 and 400, but definitely not the 800. I'm done with that distance."
"I have a holiday coming up and then a charity bike ride in Africa and there are many other things I plan to do, so maybe I'll decide after that to call it a day completely."
- Katie Ledecky