HOW TO CALIABERATE IPHONE 4S BATTERY?

Lately my iphone 4s has been shutting off at 20%.In the last question someone explained how to calibrate it but i don't think i did it right because it's still doing the same thing if someone could explain more in dept that would be great.
16 minutes ago - 4 days left to answer.

Wrong board, your in cars and matinence, but here you go anyway.

Calibrate iPhone Battery:

Use the iPhone until it it shuts OFF itself, due to Low Battery. Then Charge it back up without interruption, like unplugging it, to full charge 100%. Then before or after you do this, Reset iPhone, hold both home and power buttons until the iPhone restarts itself, ignore the "slide to power off slider", let the iPhone restart itself.

Obviously the battery was not used up from researching solutions to your dilemma with the search function… Most likely from texting and playing games…