Christians make up an estimated 2 billion people in the world (with about 1 billion Muslims and 900 million Hindus).

These statistics are from the CIA World Factbook: ( http://www.cia.gov/cia/publications/factbook/country.html )

Percentage of the United States that is Christian: 84% (Protestant 56%, Roman Catholic 28%).
The United Kingdom is made up of: 37,560,000 Christians (Anglican 27 million, Roman Catholic 9 million, Presbyterian 800,000, and Methodist 760,000)
France: 92% (Roman Catholic 90%, Protestant 2%)
Canada: 65% (Roman Catholic 45%, United Church 12%, Anglican 8%)
Japan: 0.7%
Germany: 72% (Protestant 38%, Roman Catholic 34%)
China: 1% (est)
India: 2.4%
Australia: 83% (Roman Catholic 78%, Protestant 5%)
Brazil: 70% (Roman Catholic (nominal))