Pop star Katy Perry is on the threshold of becoming the first person ever to have more than 50 million followers on Twitter.

Twitter Counter, a service for tracking Twitter usage, predicted that Perry, 29, whose Dark Horse featuring Juicy J is atop this week’s Billboard Hot 100 singles chart, would roar through the 50 million barrier sometime Friday.

On Thursday, her @katyperry account claimed 49,989,780 followers.

“Crazy, isn’t it?” said Twitter Counter in an email, adding that Perry — who tweets regularly to her fans, but follows only 130 people herself — “never really shared her Twitter milestones”.

Teen idol Justin Bieber dethroned Lady Gaga as the most followed Twitter user in January last year, but ceded the top spot to Perry in November, with US President Barack Obama in third place.

Bieber now has 49,200,172 followers who no doubt are closely following his recent run-ins with the law, including charges of driving under the influence in Florida and misdemeanour assault in Canada.

Lady Gaga, now in fourth place with 41,026,779 followers, made Twitter history when she became the first to claim 20 million followers – just under two years ago, in March 2012.

Obama, whose Twitter account is managed by Organizing for Action, the legacy of his 2012 campaign apparatus, has 41,206,151 followers.

Perry’s current album Prism entered the Billboard 200 chart at number one upon its release in October. Her dark goth-themed rendition of Dark Horse was a highlight of Sunday’s Grammy awards.