How do I calculate a share price fall as a percentage?

If a share prices is at $1200 and falls to $1050 how do I simply calculate it's fall as a percentage % ?How do I calculate a share price fall as a percentage?
1200 - 1050 = 150

150 / 1200 = 12.5%

The stock dropped 12.5%



1050 / 1200 = 87.5%

$1050 is 87.5% of what it used to be ($1200).