What time will we know the full results of the US election in UK?

The United States heads to the polls today to vote for a new president - Joe Biden's vice president Democrat Kamala Harris or former Republican president Donald Trump.

The contest is expected to be a close call, likely coming down to a razor-thin margin, with seven swing states highlighted as key battlegrounds.

Under the US voting system, a total of 270 votes in what is known as the electoral college are needed to win the presidential election. Each state holds a set number of votes based on its population, and in most cases the winning candidate takes the total.

READ MORE: Where to watch the US presidential election in UK tonight

Both Ms Harris and Mr Trump spent time during their final day of campaigning in Pennsylvania, which holds a total of 19 electoral votes and could end up deciding the winner.

At the latest polling, Ms Harris was narrowly leading over Mr Trump with 240 electoral votes to his 218. But a total of 80 votes remain uncertain.

What time will the election results come out in the UK?

For Brits wanting to stay up to watch the results come in, it is likely to be a long night and even if you last until the following morning you're not guaranteed to hear the winner.

Due to the different times zones across America, polls will close at different points during the night. The first polls to close, including the first swing state - Georgia, will be at midnight UK time. Further polls will then close on the hour right through until 6am, when Alaska concludes its voting.

Once a poll closes, broadcasters can project the winner - as they would in an exit poll during general elections in the UK.

However, not all states may be called as soon as polls close. For some of the most tightly-contested states, it may take much longer to make a projection and networks will likely to decide to hold off on calling a winner until votes have been counted.

For that reason it may take hours, or even days until we know who the next president will be.

When did previous US election winners get declared?

In 2020, Pennsylvania was the state that gave Mr Biden enough votes to guarantee he would be president. However, the result there was not called for Mr Biden by most of the US networks until the Saturday after the election, meaning it took four days from polling day to have the winner confirmed.

Other times, the winner has been announced much sooner. In 2016, Mr Trump was declared the winner shortly before 8am in the UK the day after the election.

At the election before that, in 2012, Barack Obama's victory was projected before midnight on polling day, which is around 5am in the UK.

With this year's election being such a close contest, it's likely that we could be in for a longer wait.