Net cash proceeds of the deal after tax and a £0.4bn reinvestment to retain a 40% stake in Kantar will amount to US$3.1bn.
"Kantar has the advantage of being relatively self-contained and so can be split off from the parent with minimal restructuring costs ... the proceeds of the sale will drop straight through to the balance sheet and shareholders pockets", Nicholas Hyett, Equity Analyst at Hargreaves Lansdown, said.
Launched by WPP in 1992, Kantar offers insights into the views of customers and consumers in over 100 countries.
WPP chief executive Mark Read said: 'This transaction creates value for WPP shareholders and further simplifies our company.
Sources familiar with the situation had told Reuters that private equity groups including CVC, Apollo and Bain had submitted preliminary bids for Kantar.
The company has agreed to sell 60% of Kantar to private equity firm Bain Capital in a deal that valued the business at around $4bn including debt.
The deal will be marginally dilutive to its headline earnings per share in 2021, and its dividend policy will remain unchanged as a result of the transaction.
Private equity firm Bain Capital are to acquire a 60% stake in Kantar in an expected £2.5bn worth proceeds going to WPP however, the overall value of Kantar will be £3.2bn.
Kantar CEO Eric Salama said last month that a new majority owner could look for ways to speed up its time to market for data and services, drive growth with existing clients and move its business more into digital activities. With Bain Capital as a partner who shares its ambition and brings relevant expertise, Kantar can accelerate its growth and impact for its clients, he explained. Completion of the deal is expected to occur in early 2020.
"We will invest in technology to expand the company's capabilities and reinforce its global leading position", he added. "Our deep sector knowledge, operational expertise and strong track record of partnering with management teams to accelerate growth give us confidence that we can help Kantar grow both organically and by acquisition".