Only about one of every three Presidents historically (14 of 44) through Inauguration Day 2021 has served two terms:
Ulysses S. Grant
Franklin D. Roosevelt
Dwight D. Eisenhower
George W. Bush
Additionally, 7 others served more than one term, but not two complete terms:
Lyndon B. Johnson
And only Lincoln, McKinley, and Nixon were actually elected to two terms, so a total of 17 Presidents elected twice, while TR, Coolidge, Truman, and Johnson succeeded after deaths of their predecessor, and were only elected once to the Presidency.
So a total of 21 Presidents served more than four years, although Lincoln and McKinley for just a few months more, and Coolidge, Johnson and Nixon only months more than a year. So only TR and Truman were very close to two complete terms. Ultimately, 16 out of 44 basically served two terms.
Now we can add Joe Biden to the list of those who will not serve two terms or even be elected a second time, as with the Afghanistan debacle, it seems certain that he will not run again in 2024!