The brand is spending big ahead of the start of the Rugby World Cup, of which its rival Heineken is the official beer partner, next week.
The reach estimate is provided by Guinness' media agency Carat, which worked on the campaign with creative agency Abbott Mead Vickers BBDO.
The ad, featuring former Wales rugby player Gareth Thomas, is one of two 60-second spots celebrating stories of character and integrity from the world of rugby.
Thomas, who played more than 100 times for Wales, hid his sexuality from his teammates until he came out as gay in 2009.
The ad is a cut-down version of a four-minute film about Thomas’ fear of rejection from the world of rugby because of his sexuality. It celebrates his courage and the empathy shown by his teammates when he came out.
The film was launched online on Guinness Europe’s rugby YouTube channel on Monday and has now been viewed 167,000 times.
The other ad is a cut-down version of a film about former South African player Ashwin Willemse, who succeeded despite a deprived background and an early life of crime.
Nick Britton, marketing manager for Guiness Western Europe, said: "We are delighted to be able to shine a light on these two stories of integrity and character from the world of rugby. We’re also proud to be able to showcase them to so many people at the same time."
Guinness is a partner of the England, Ireland, Wales and Scotland rugby teams and the offical beer of the RBS 6 Nations.