How to calculate percentage change?

I am currently working on an assignment i have got a set of results before and after and I need to calculate the percentage change? For example 0.31 and 0.33 how would I work that out?How to calculate percentage change?
(final - initial)/initialHow to calculate percentage change?
((final value - initial value) / initial value)-1) x 100%. example initial value 4 and final value 5 gives as follows :-
( (5-4) /4) x100% = 100(1/4) = +25 %
Trying it the other way round with initial value 5 and final value 4 gives :-
100( (4-5)/5) = 100( -1/5) = -20%.
SECOND METHOD
If you have a situation where the initial value remains unchanged(such for example the elongation of a 10 cm long spring as it is loaded0 then you simply take the old value from the new then divide by the initial 10 and multiply by 100 to get a percentage.This boils down to actual change from INITIAL multiplied by 100/(Initial un-extended length) giving finally % change from initial = 10(final -initial)
It is woth you studying this second method if you have a great amount of data ,you just work out the multiplier(10 in my example from 100/(initial gauge length and multiply each subsequent extension by it.
If this is just a one off for you then the first method will do.How to calculate percentage change?
Did you tried the Delta of them?

%final-%initial