Every football fan will claim their club is the biggest in the world, but how is the size of a club truly measured?

Is it based on history? Do more trophies make one team bigger than another? Or perhaps it's based on current form - are Liverpool and Manchester City now England's top two clubs?

It all comes down to opinion of course and many supporters will have their own argument that backs up their own side. 

But another way clubs could be ranked is on social media followers.

Like it or not, being popular on Twitter, Instagram and Facebook is a big part of modern football. 

So which teams are the biggest in the world based on their online following? Check out the top 20 below (all figures accurate at the time of writing on 17/10/2019): 

20) Boca Juniors - 16,285,317 followers 
19) Fenerbache - 20,851,270 followers
18) Corinthians - 21,517,168 followers
17) Tottenham - 21,787,868 followers
16) Flamengo - 22, 995, 937 followers
15) Inter Milan - 23,072,360 followers
14) Atletico Madrid - 26,562,835 followers
13) Borussia Dortmund - 26,882,383 followers
12) Galatasaray - 29,177,682 followers
11) AC Milan - 38,225,441 followers
10) Manchester City - 60,718,505 followers
9) Liverpool - 67,883,909 followers
8) Arsenal - 68,650,732 followers
7) Paris Saint-Germain - 70,067,458 followers
6) Bayern Munich - 72,855,574 followers
5) Juventus - 79,422,589 followers
4) Chelsea - 80,475,417
3) Manchester United - 125,255,379 followers
2) Barcelona - 211,914,075 followers
1) Real Madrid - 222,471,779 followers 

There we have it, the biggest teams in the world based on social media following across Twitter, Instagram and Facebook. 

Interestingly, a majority of every club's followers come from Facebook, with Twitter usually being the platform they have the least amount of fans on. 

It's also crazy to see just how far ahead the top two - Real and Barca - are ahead of every other team. 

No wonder El Clasico is considered the biggest fixture in the world, given how much interest both Spanish sides have. 

But does their dominance on social media make Madrid and Barcelona the two biggest clubs in the world? Some fans will agree, while many of course, will not.