May needs the backing of two-thirds of lawmakers and said she would put her election call to the House of Commons today.
Professor John Curtice from Strathclyde University, who conducted the analysis for the Daily Telegraph, said that Labour's collapse under Jeremy Corbyn helped explain the results.
Labour's marginal seats in the West Midlands, on the edge of Northern cities and in London suburbs are believed to be the most likely to fall to the Tories. Conservative Party board members have told the Daily Telegraph that they want a "decapitation strategy" targeting Labour heartland seats in the North.
It would replicate the ruthless campaign against the Liberal Democrats in the 2015 election in which the Tories took many seats off their coalition partners.
A recent poll of polls put the Conservatives on 43 per cent of the vote and Labour on 27 per cent - a Tory lead of 16 points. Ukip and the Lib Dems were both on 10 per cent.
If that voting occurred at the election and the swing was equal across Britain, the Tory majority would rise to an estimated 100 seats.
Curtice said: "Theresa May wins seats from the Labour Party. Why? Because Labour is at sixes and sevens, Jeremy Corbyn is not a very popular leader and the party is divided over Brexit whereas Mrs May seems to be at least reasonably popular.
"Some of the leadership research recently has found she's not loved, but respected."
He added that the massive majority for the Tories suggested by their poll lead would, in reality, likely be far smaller.
"Although Mrs May goes into this election with an enormous lead over Labour, she is not guaranteed to secure the overwhelming majority that she evidently hopes to secure," he said.
"The SNP remain dominant in Scotland and are likely to retain most of the 56 seats that they already hold. Therefore any majority has to be acquired through winning seats in England and Wales alone. Meanwhile, there are relatively few marginal seats - many of Labour's seats have large majorities that could render them invulnerable, even in the event of a disastrous performance nationwide."
The Prime Minister yesterday hinted that she would put her leadership credentials and the perceived weakness of Corbyn at the heart of her campaign pitch.
May said "the decision facing the country will be all about leadership" and warned against "a weak and unstable coalition government led by Jeremy Corbyn".
What's at stake?
Why did Theresa May make her move?
May took power in July, after David Cameron resigned following Britain's vote to leave the European Union. A new ballot offers her the chance to seek her own mandate and to increase the Conservative Party's narrow majority in the House of Commons, where it holds 330 of 650 seats. Britain formally triggered the process for leaving the EU last month, but more turmoil is in store as the country negotiates a divorce that will affect every aspect of life in Britain.
Is it a done deal?
British prime ministers used to have the power to call elections at will, but the Fixed-Term Parliaments Act, passed in 2011, makes things more complicated. Under the act, national elections are held every five years, in May. The Prime Minister can call an early election if two-thirds of lawmakers support it. May will ask the House of Commons to vote on the snap election today. Jeremy Corbyn, leader of the main opposition Labour Party, has said he welcomes an election, meaning the election call will almost certainly pass.
What's at stake?
Negotiations to leave the EU will be arduous. The talks will deal with money, trade, defence, to name but a few key topics. If May were to gain more seats, she would be able to have more freedom to pursue her own agenda, and to neutralise those inside and outside her own party who disagree with her positions.
How does it work?
Britain has 650 constituencies from which voters select a local MP. The party with the most MPs wins a working majority and is allowed to install its leader as prime minister.
Who could win?
Opinion polls released last weekend showed the Conservatives with a double-digit lead over the Labour Party, which has been weakened by a split between moderates and left-wing leader Jeremy Corbyn.
Are there risks?
Anytime a leader goes to the people for a vote, there are risks, as Cameron learned to his peril when he lost the vote on Britain's departure from the EU just over a year after winning re-election.
