The Isle of Wight has the biggest electorate at about 108,000 (in 2018), while Na h-Eileanan an Iar in Scotland has the smallest number at just over 21,000 (in 2017). The average UK constituency has about 71,000 voters in it.
The House of Commons Library has a searchable tool of constituency data here.
This article is part of our Ask Full Fact series on the 2019 general election, answering your questions about the election, from claims the main parties are making to what happens on polling day.
You can see all the questions we’ve answered so far and we’ll keep adding to it as we get through them.