A variety of factors, including size of support, wealth, standard of stadium, current standing and historic success.
We've taken all these aspects into account – giving more weight to current situation than the past (with less and less importance attached to events as you delve further into the history books) – and come up with a ranking of the top 30 biggest football clubs in Britain.
Inevitably there are areas of dispute and clubs who narrowly missed out on making the cut.
Take a look and let us know your opinion by leaving a comment below.