A-levels will be checked to see whether they match the difficulty of equivalent exams in China, India, Canada, Singapore, South Korea, Australia, New Zealand and at least one European country.
The major international study unveiled by Ofqual, the exams regulator, is expected to begin by exploring standards in history, chemistry and maths A-levels. It could later be extended to cover other subjects and countries and to look at GCSEs and Sats as well as A-levels.
Kathleen Tattersall announced the study in one of her last acts before resigning as Ofqual chair and chief regulator last Friday.
She explained that the study was a response to the "challenge" laid down by Education Secretary Michael Gove, who has said that he wants England's exams subjected to international comparisons.
Ms Tattersall said: "In the global economy, it is increasingly important that we look to other countries for ideas and good practice, and to ensure that our qualifications system can compete with the best in the world."
She said she had decided to resign from Ofqual because of a "fresh perspective to public policy" under the coalition Government.
Responding to her departure Mr Gove said he wanted to further strengthen Ofqual's independence by making the chief regulator a full-time crown appointment, with executive responsibility for the watchdog.
The Conservatives indicated last year that they were considering a reduced role for Ofqual, possibly removing its A-level accreditation responsibilities.
Labour ministers were accused of cronyism by Douglas Carswell, a Conservative member of the Commons schools committee, when Ms Tattersall was appointed to Ofqual in 2008, because she was a Labour party member.
On Friday Ms Tattersall said: "I have come to the conclusion that it is in the best interests both of Government and of the education sector for Ofqual to have a new chair."