The channel beat its daily reach record on Sunday 10 August, with viewers watching swimming, diving, gymnastics and basketball events. The previous record for the channel was 41.1 million viewers on 20 January 2008.
Over last weekend, the average audience per quarter of an hour was 13% higher than during the first weekend of the Olympic Games in Athens 2004.
Meanwhile, BBC One's highlights of Sunday's Olympics coverage, in which British divers Blake Aldridge and Tom Daley saw their medal hopes dashed, netted 4.4 million viewers.
The highlights package captured a 21.9% share of the audience between 7pm and 8pm. Earlier in the day, BBC One's live coverage of the Games was watched by 2.2 million viewers and a 26.2% share of the audience between 12.45pm and 5.15pm.