The group, which is part of the John Lewis Partnership, said it reached the milestone on a rolling 52-week basis, having recently revealed that sales through johnlewis.com soared 41% to £959 million in 2012 and accounted for a quarter of trade.
It is the latest retailer to highlight the shift towards online shopping after Tesco said, on presenting annual results last week, that it was scrapping more than 100 planned UK store developments under aims to focus more on internet sales.
The UK's biggest supermarket said online sales reached £3 billion after rising 13% in the year to February 23.
Department store Debenhams also hailed a surge in online sales - up 46% in the six months to March 2 - which helped offset falling high street trade amid the snow and adverse weather earlier this year.
John Lewis had expected online sales to reach the £1 billion mark in 2014, but IT director Paul Coby said the group was seeing "an unprecedented pace of online growth".
The new website allows customers to build a "wish list" of products and includes a search history.
With online mobile access now accounting for more than 25% of traffic to johnlewis.com, the retailer has also revamped its mobile offer and plans to launch a new app later this year.