The ICC formally adopted the Duckworth Lewis Stern (DLS) method, which is a formula to fairly calculate the winning side when inclement weather intervenes and the match is interrupted, which includes re-calculating totals when time is lost in the match.
The following documents explain the methodology of Duckworth Lewis Stern and any questions you may have.
Duckworth Lewis Stern Methodology
Duckworth Lewis stern Standard Edition table
The DLS Methodology Frequently Asked Questions
Duckworth Lewis Stern Calculator