When we will know who Pope Francis' successor is as funeral takes place in the Vatican City

The passing of Pope Francis means a new head of the Catholic Church will soon be elected.

The 88-year-old died on April 21 - Easter Monday - after suffering a stroke following a period of ill health.

The funeral for Pope Francis, whose real name was Jorge Mario Bergoglio, is set to take place in St Peter's Square in Rome on Saturday (April 26).

He became Pope back in 2013 ​after the previous Pope, Benedict XVI, resigned due to old age.

Pope Benedict stepped back on 28 February, while Pope Francis was elected 13 days later, on 13 March 2013.

But as reigning Pope Francis died rather than stepped back, it's going to take longer than 13 days from his death for a new pope to be decided.

What happens next is the secret meeting of cardinals, which usually begins between 15 and 20 days after a pope’s death.

Known as the conclave, it could begin between May 6 and May 11.

However, Joe Ronan, who works with the Catholic Voices media charity, told reporters that if cardinals agree, then it could begin earlier.

He added that following the nine-day period of mourning and the Pope's funeral, May 5 seems a likely date on which it might start.

How is the new pope decided on?

Pope Francis died on April 21 (Buda Mendes/Getty Images)

A two-thirds majority is required for a new pope to be elected, and only cardinals - senior members of the Catholic Church - who were aged 80 or under on the day of the Pope’s death have a say.

There must be a minimum of 120 cardinals in the conclave. Currently, there are around 135 cardinals of voting age.

The conclave will convene in the Sistine Chapel, where there can be up to four votes each day.

Ronan explained: “It could conceivably go on for quite some time.”

However, he said there is 'no set time' for the conclave to elect a new pope.

If it carries on for a long time, it is possible for the cardinals to take a break, and have a non-voting day, he added.

People have been paying their respects to Pope Francis at St Peter's Square (Christopher Furlong/Getty Images)

Each time there is a vote, the ballots are then burned with black smoke from a chimney of the Sistine Chapel indicating no-one has been elected and white smoke confirming a new pontiff.

Ronan said there is expected to be a double confirmation, to avoid confusion: “As well as the white smoke I think they will also ring the bells of St Peter’s as a double check.

“These days they go to great pains to make sure that the colour of the smoke is very clear, sometimes (in the past) you have had a sort of grey colour.”

Once a new pope accepts his election, it is usual that he would appear 'relatively rapidly' on the front balcony of St Peter’s Basilica which overlooks the square.

An announcement in Latin of 'Habemus Papam' - meaning 'we have a Pope' is made alongside the new pontiff’s appearance.