Q: How to check the amount of time battery is utilized from last charge?

  Charge the battery to full. Disconnect the Mac from power.

  Applications > Utilities > Activity Monitor

  Click the “Energy” tab.

• Time on Battery: The time elapsed since your portable Mac was unplugged from AC power.

  https://support.apple.com/en-us/HT201464

Hitout22 wrote:

 

I am not getting 12 hours battery back up as apple promised. I am getting around 7-8 hours.

Apple does not promise you 12 hours of battery run time.  Read very carefully and you will note that they say UP TO, not will.

Ciao.