He was educated at Oundle School and Jesus College, Cambridge.
In 1929/30, he was Captain of Jesus College Boat Club, and he rowed in the winning Cambridge crews of the Boat Race in 1930 and 1931 races. Carpmael married Anne Wise, widow of Jock Wise. Prior to her death in 2003 she established a Charitable Trust to preserve the house and riverside land as Withymead nature reserve.
He led a team for two years running to Australia where they won easily against extremely tough opposition. Carpmael joined London Rowing Club and in 1948 was the first winner of the Norfolk Sculls. He won the Wingfield Sculls in 1948 and 1949. Carpmael was still rowing at the age of 70 against his sons, one of whom also won the Wingfield Sculls.