Born in Chelsea, London, she trained at the Margaret Morris School of Dancing, and performed from the age of ten, performing with Ellen Terry in Crossings. She gained her first film role at the age of 12, in The Arcadians (1927), also known as The Land of Heart's Desire.

Calvert performed in repertory theatre in Malvern and Coventry. She made her London stage debut in A Woman's Privilege in 1939. Her early films include Two Days to Live (1939).

Calvert was in a war movie, Neutral Port (1940), then had a good role as Michael Redgrave's love interest in Kipps (1941), directed by Carol Reed. After a detective film Inspector Hornleigh Goes To It (1941) she had the co-lead in Uncensored (1942),a war movie with Eric Portman. Reed used her again in The Young Mr Pitt (1942), playing Eleanor Eden.

In 1942, she had the lead role as Patricia Graham in the West End production of Terence Rattigan's play Flare Path.

She was married to the actor and antiquarian bookseller Peter Murray Hill, with whom she had two children, Ann Auriol (born 1943) and Piers Auriol (born 1954). She died in her sleep in London in 2002, from natural causes, aged 87.

Calvert followed it with Fanny by Gaslight (1944), co-starring Granger and Mason, and another big hit. Also popular was Two Thousand Women (1944), made by Launder and Gilliat, about British women interned in occupied France. It co-starred Patricia Roc, who appeared with Calvert and Granger in Madonna of the Seven Moons (1945), another Gainsborough melodrama, and another hit. Calvert's successful run at the box office when she and Mason were reunited in They Were Sisters (1945), a more contemporary-set Gainsborough melodrama. Exhibitors voted her the fifth most popular star of 1945 in Britain.

She was one of Stewart Granger's loves in The Magic Bow (1946) and had the female lead in a drama about colonialism in Africa Men of Two Worlds (1946), made a few years before being released. It was a success, though not profitable because of its high cost. The Root of All Evil (1947) was one of the last of the Gainsborough melodramas. She was voted the sixth most popular British star at the box office in 1946.

Calvert's success had been noticed in the US, although her films had not been as popular there. Universal signed her to star in Time Out of Mind (1947), which was a box office disappointment. She received several offers from studios and eventually decided to sign a six-picture deal with Paramount.

She returned to Britain to make Broken Journey (1948) playing a role written especially for her, but the film lost money.

Calvert went to Hollywood to make two films, both for Paramount: My Own True Love (1949), with Melvyn Douglas, and Appointment with Danger (1951 but made two years earlier) with Alan Ladd, playing a nun. She did Peter Pan on stage in Britain.

Back in Britain she made two films with Director Ladislao Vajda, neither particularly successful: Golden Madonna (1950), shot in Italy, and The Woman with No Name (1950). She invested her own money in the latter. She wanted to produce other films: Eastward Ho, about an Englishwoman who romances a Cowboy, and Equilibrium, about a trapeze Artist, as well as star in a third film for Paramount but none of these were made.

Calvert was in a thriller Mr. Denning Drives North (1951) with John Mills and a BBC TV production The Holly and the Ivy (1951). She had her first big hit in a while, Mandy (1952).

Calvert was a wife in The Net (1953) then was off screen for a while. He acted on stage in It's Never Too Late (1956), then appeared in the film version. She followed it with Child in the House (1956).

Calvert had a support part in the Hollywood financed Indiscreet (1958) then played a concerned mother in The Young and the Guilty (1958) and a wacky spinster in A Lady Mislaid (1959). On TV she was in "The Break" for Armchair Theatre (1959) and played Katherine O'Shea in Parnell for Play of the Week (1959), then reprised her role as Mrs March for the BBC in Good Wives (1959). She was Constance Wilde in Oscar Wilde (1960) with Robert Morley and A Righteous Woman on Play of the Week (1962).

She acted in over 40 films, her later films including The Battle of the Villa Fiorita (1965),Twisted Nerve (1968), Oh! What a Lovely War and The Walking Stick (1970).

In 1970–72, she starred in her own TV series, playing the part of an agony aunt with problems of her own in Kate.

She made TV appearances in programmes such as Crown Court, Ladykillers, Tales of the Unexpected, Boon, After Henry and Limelight: The Film Years – The Lime Grove Story. She also played D.I. Barnaby's Aunt Alice (Alice Bly) in a Midsomer Murders episode "Blue Herrings" in 2000. She was the subject of This Is Your Life in 1972 when she was surprised by Eamonn Andrews.