Shares in both firms were up today as the two companies recommended the offer to their respective shareholders.
For each UBM share, stakeholders will receive 1.083 new Informa shares and 163p. Based on the last closing price of Informa shares, this values UBM at £3.9bn.
The enlarged group will create a leading business-to-business (B2B) information services group, Informa said today.
"It is clear that the B2B market is moving to operating scale and industry specialisation," said Stephen Carter, chief executive of Informa.
"Our recommended offer for UBM promises to create a leading B2B information services group with the international reach and market capabilities to take full advantage of these trends."
The company expects to realise £60m in annualised cost savings from the integration of UBM, with the unification of the businesses expected by the end of the year.
Carter added: "We will seek to operate with speed and purpose through an accelerated integration plan that unifies management, combines our businesses and adopts a focused approach to industry specialisation."
Shares in Informa were up 1.6 per cent today at 698p, though they are still below the 746p price which was used to agree the offer.
Meanwhile UBM's share price was up 4.3 per cent to 907p, having jumped almost 100p in a day when Informa's offer was announced.