How do you calculate the follow on score in test cricket?

Answer 1

The number of runs by which a team must lead to enforce follow-on upon its opponent is determined by Law 13 of the Laws of cricket, which takes the length of the match into consideration:

In a match of five days or more, a side which bats first and leads by at least 200 runs has the option of requiring the other side to follow-on.

in one of three or four days, 150 runs;

in a two-day match, 100;

in a one-day (two-innings per side) match, 75.