Half your age plus 7. That is your dating range.
So, if you are 20y = X
X = 20/2 + 7
X = 17
I am 27...
27y = X
X = 27/2 + 7
X = 13.5 + 7
X = 20.5
Therefore the Lower limit of my dating range is 20.5 years old.
Or take your age, subtract 7 and multiply by 2 to see the top end.
So.. (20yrsold -7) x 2 = X
13 x 2 = 26, therefore a 20 year old can date at oldest someone who is 26.
I'm 27, so (27 - 7) x 2 = 40. The older people get the less they care what the range is but I think the Math is okay.
That is a rule but, since I'm not really dating I don't have any rules.