Richard, who has sold more than 250 million records in a 52-year career, was taking a day off from his run of shows at London's Royal Albert Hall.
"For the 70th, even when it comes to a birthday party, I'm not going to have a big party on the day. I'm going to have a quiet night," he told ITV television.
He said his family were coming over "and we're going to have an Indian curry."
The singer was born Harry Webb in Lucknow, northern India, on October 14 1940.
Cliff Richard and The Shadows were a landmark act in early British rock and roll, with Richard being dubbed England's answer to Elvis Presley.
Indeed, he and Presley are the only acts to make the British singles charts in every decade.
He has also been nicknamed the Peter Pan of Pop for his enduring youthful looks and appeal.
A committed Christian who shunned the sex, drugs and alcohol lifestyle, in 1995 he became the first rock star to be knighted.
Outside Britain, he retains a following in Australasia, southeast Asia and Japan, South Africa, Canada and northern Europe.
His hits include "Move It" (1958), "Living Doll" (1959), "The Young Ones" (1962), "Summer Holiday" (1963), "Congratulations" (1968), "Devil Woman (1976), "We Don't Talk Anymore" (1979), "Mistletoe and Wine" (1988) and "Saviour's Day" (1990).
